Pengguna:Dedhert.Jr/Uji halaman 03/4

Simbol matematika merupakan simbol atau kumpulan darinya yang digunakan untuk menyatakan suatu objek matematika, tindakan objek matematka, kaitannya dengan objek matematika, atau membangun simbol-simbol lain yang muncul di suatu rumus. Sebagai rumus yang dipenuhi dengan simbol-yang beragam, banyak simbol diperlukan untuk mengekspresikan matematika.

Simbol paling dasar yang digunakan dalam matematika adalah digit desimal (0, 1, 2, 3, 4, 5, 6, 7, 8, 9), dan huruf berupa alfabet Latin. Digit desimal digunakan untuk menyatakan bilangan melalui sistem Hindu–Arabic. Menurut sejarah, huruf kapital digunakan untuk menyatakan titik di dalam cabang geometri, sedangkan huruf kecil dgunakan sebagai variabel dan konstanta. Huruf digunakan untuk merepresentasikan banyak jenis objek matematika lainnya. Seiring dengan jumlah jenis simbol matematika yang sangat meningkat pesat dalam matematika modern, huruf Yunani dan beberapa huruf Ibrani juga digunakan. Dalam rumus matematika, rupa huruf yang standar untuk huruf Lati maupun huruf kecil Yunani dimiringkan, sedangkan huruf kapital Yunani tidak dimiringkan. Karena jumlah simbol yang semakin banyak, rupa huruf lainnya juga digunakan seperti rupa huruf yang ditebalkan $\mathbf {a,A,b,B} ,\ldots$, rupa huruf script ${\mathcal {A,B}},\ldots$ (huruf kecilnya jarang digunakan karena tampilannya yang dapat membingungkan dengan rupay huruf yang standar), fraktur Jerman ${\mathfrak {a,A,b,B}},\ldots$, dan blackboard bold $\mathbb {N,Z,Q,R,C,H,F} _{q}$ (huruf yang lain jarang digunakan, atau pemakaiannya belum dilaksanakan secara konvensional).

Penggunaan huruf Latin dan huruf Yunani sebagai simbol yang menyatakan objek matematika tidak dijelaskan dalam artikel ini. Untuk pemakaiannya, lihat Variabel (matematika) dan Daftar tetapan matematis. Akan tetapi, beberapa simbol yang dijelaskan disini memiliki bentuk yang sama seperti huruf, dan simbol-simbol tersebut berasal dari huruf Latin maupun huruf Yunani, contohnya seperti $\textstyle \prod {}$ dan $\textstyle \sum {}$.

Huruf-huruf tersebut masih belum cukup untuk keperluan matematikawan, dan banyak simbol-simbol lainnya digunakan. Beberapa simbol aslinya diambil dalam tanda baca dan diakritik yang biasanya digunakan dalam tipografi. Selain itu, ada beberapa simbol matematika yang dibuat dengan mengubah rupa bentuk huruf, contohnya seperti $\in$ dan $\forall$. Adapula simbol-simbol lain, seperti + dan =, dirancang secara khusus untuk matematika.

Tampilan artikel ini

Entri glosarium biasanya memilki struktur yang didasarkan pada topik secara abjadiah. Akan tetapi, artikel glosarium ini tidak demikian, karena tidak ada urutan simbol yang dilakukan secara natural. Selain itu, banyak simbol yang digunakan dalam berbagai bidang matematika dengan pengertian yang berbeda, sama sekali tidak ada kaitannya. Oleh karena itu, simbol-simbol yang diringkas di bawah diurutkan secara acak.

Artikel ini dibagi menjadi bagian-bagian yang diurutkan berdasarkan tingkat keteknisan yang tinggi. Ini berarti, bagian pertama menjelaskan simbol-simbol yang dijumpai dalam kebanyakan buku matematika, dan bagian pertama seharusnya diketahui oleh pembaca yang memulai matematika. Di sisi lain, bagian terakhir menjelaskan simbol-simbol yang digunakan secara khusus untuk cabang matematika sahaja. Meskipun demikian, bagian yang membahas tentang tanda kurung diletakkan di bagian akhir artikel, walaupun kebanyakan entri di bagian tersebut bersifat elementer. Urutan bagian artikel menjadi lebih mudah untuk mencari entri simbol yang diinginkan dengan scrolling.

Kebanyakan simbol memiliki banyak pengertian yang galibnya dibedakan berdasarkan cabang matematika, dan simbol-simbol tersebut digunakan berdasarkan sintaks, yang berarti berdasarkan posisinya di dalam sebuah rumus dan kealamian bagian rumus lainnya yang saling dekat dengannya. Yang dimaksud pengertian simbol bergantung pada sintaks, berarti bahwa sebuah simbol mungkin memiliki entri yang berbeda tergantung sintaksnya. Untuk meringkas sintaks di dalam nama entri, simbol $\Box$ digunakan untuk menyatakan bagian yang berdekatan dari suatu rumus yang mengandung simbol. Lihat § Tanda kurung untuk contoh pemakaiannya. Pembaca ingin mencari simbol di suatu cabang matematika, tetapi kemungkinan belum memahami cabang matematika tersebut; karena itu, simbol yang memiliki pengertian yang berbeda dikelompokkan ke dalam bagian dengan simbol yang memiliki pengertian umum.

Hampir semua simbol memilki dua versi cetak. Versi cetak simbol tersebut dapat ditampilkan sebagai karakter Unicode, atau dalam format LaTeX. Simbol dengan versi Unicode membuat pencarian mesin beserta salin dan tempel (copas) semakin mudah digunakan. Di sisi lain, rendering pada LaTeX sering kali terlihat lebih estetik, dan secara umum dianggap sebagai versi cetak yang standar dalam kalangan matematika. Oleh karena itu, artikel ini menggunakan simbol berupa versi Unicode (bila memungkinkan) untuk melabeli entrinya, dan versi LaTeX digunakan di dalam deksripsinya. Jadi, untuk mencari bagaimana mengetik simbol di LaTeX, cukup lihat sumber artikelnya.

For most symbols, the entry name is the corresponding Unicode symbol. So, for searching the entry of a symbol, it suffices to type or copy the Unicode symbol into the search textbox. Similarly, when possible, the entry name of a symbol is also an anchor, which allows linking easily from another Wikipedia article. When an entry name contains special characters such as [, ], and |, there is also an anchor, but one has to look at the article source to know it.

Finally, when there is an article on the symbol itself (not its mathematical meaning), it is linked to in the entry name.

Operator aritmetika

+

1.  Melambangkan penambahan dan dibaca plus atau ditambah; sebagai contoh, 3 + 2.

2.  Melambangkan bahwa suatu bilangan positif dan dibaca plus. Simbol ini tidak perlu digunakan, melainkan untuk menyatakan bahwa suatu bilangan itu bernilai positif, khususnya ketika bilangan lain di suatu konteks dapat berupa negatif; sebagai contoh, +2.

3.  Terkadang digunakan sebagai pengganti $\sqcup$ untuk gabungan lepas dari himpunan.

–

1.  Melambangkan pengurangan dan dibaca dikurang; sebagai contoh, 3 – 2.

2.  Melambangkan invers aditif dan dibaca negatif; sebagai contoh, –2.

3.  Sebagai pengganti \ untuk melambangkan komplemen (teori himpunan) suatu himpunan; lihat \ di § Teori himpunan.

×

1.  Dalam aritmetika elementer, simbol tersebut melambangkan perkalian, dan dibaca dikali; sebagai contoh, 3 × 2.

2.  Dalam geometri dan aljabar linear, simbol tersebut melambangkan darab vektor (cross product).

3.  Dalam teori himpunan dan teori kategori, simbol tersebut melambangkan hasil kali Cartesius dan darab langsung. See Lihat pula × di § Teori himpunan.

·

1.  Melambangkan perkalian dan dibaca dikali; sebagai contoh, 3 ⋅ 2.

2.  Dalam geometri dan aljabar linear, simbol ini melambangkan darab bintik (cross product).

3.  Sebagai gambaran sementara yang digunakan untuk menggantikan elemen yang belum ditentukan. Sebagai contoh, "nilai mutlak dilambangkan sebagai | · |" mendeskripsikan lebih jelas daripada mengatakan "nilai mutlak dilambangkan sebagai | |.

±

1.  Melambangkan tanda plus atau tanda minus.

2.  Melambangkan jangkauan nilai yang dimiliki suatu kuantitas; sebagai contoh, 10 ± 2 melambangkan nilai tak diketahui yang berada di antara 8 dan 12.

∓

Digunakan sebagai pasangan ±, yang melambangkan tanda berlawanan. Maksudnya adalah + jika ± adalah –, dan – jika ± adalah +.

÷

Simbol ini sangat luas digunakan untuk melambangkan pembagian dalam negara yang menggunakan bahasa Inggris. Walaupun demikian, simbol ini tidak lagi digunakan dalam matematika dan "tidak direkomendasikan" untuk menggunakannya. Namun dalam beberapa negara, simbol ini mengindikasikan pengurangan.

:

1.  Melambangkan perbandingan dari dua kuantitas.

2.  Dalam beberapa negara, simbol tersebut melambangkan pembagian.

3.  Dalam notasi ungkapan himpunan, simbol tersebut digunakan sebagai pemisah, yang berarti "sehingga". Lihat (□ : □}.

/

1.  Melambangkan pembagian. Operator ini sering kali diganti dengan garis horizontal. Sebagai contoh, 3/2 atau ${\tfrac {3}{2}}$.

2.  Melambangkan struktur kuosien. Sebagai contoh, himpunan kuosien, grup kuosien, kategori kuosien, dan lain sebagainya.

3.  Dalam teori bilangan dan teori lapangan, $F/E$ menyatakan perluasan lapangan, dengan F menyatakan lapangan perluasan dari lapangan E.

4.  Dalam teori probabilitas, simbol tersebut melambangkan probabilitas bersyarat. Sebagai contoh, $P(A/B)$ melambangkan peluang A dengan B terjadi. Alternatif notasi dari probablitas bersyarat adalah $P(A\mid B)$, yang dapat dijelaskan di "|".

√

Melambangkan akar kuadrat dan dibaca akar kuadrat dari. Namun, simbol ini jarang digunakan dalam matematika modern karena tidak ada garis horizontal di bagian atasnya (lihat di entri berikutnya). Sebagai contoh, √2.

√  

1.  Melambangkan akar kuadrat dan dibaca akar kuadrat dari. Sebagai contoh, ${\sqrt {3+2}}$.

2.  Dengan bilangan bulat yang lebih besar daripada 2, yang merupakan superskrip di sebelah kirinya, melambangkan akar pangkat ke-n. Sebagai contoh, ${\sqrt[{7}]{3}}$ melambangkan akar pangkat ke-7 dari 3.

^

1.  Eksponensiasi biasanya dilambangkan dengan superskrip. Akan tetapi, $x^{y}$ acap kali dilambangkan x^y ketika superskrip tidak ditampilkan, seperti dalam bahasa pemrograman (di antaranya LaTeX) atau plain text email.

2.  Bedakan dengan ∧.

Kesamaan, ekuivalensi, dan kesebangunan

=

1.  Melambangkan kesamaan.

2.  Digunakan untuk menamai suatu objek matematika seperti kalimat "misalkan $x=E$", dengan E adalah ekspresi. Di papan tulis dan di beberapa buku ajar matematika, simbol ini dapat disingkat sebagai $x\,{\stackrel {\mathrm {def} }{=}}\,E$ atau $x\triangleq E.$ Simbol ini memiliki kaitan dengan konsep assignment dalam ilmu komputer, yang dilambangkan berbagai macam simbol (tergantung bahasa pemrograman yang digunakan) seperti $=,:=,\leftarrow ,\ldots$

≠

Melambangkan ketaksamaan dan mengartikan "tidak sama dengan".

≈

Mengartikan "kira-kira sama dengan". Sebagai contoh, $\pi \approx {\frac {22}{7}}$.

~

1.  Between two numbers, either it is used instead of ≈ to mean "approximatively equal", or it means "has the same order of magnitude as".

2.  Denotes the asymptotic equivalence of two functions or sequences.

3.  Often used for denoting other types of similarity, for example, matrix similarity or similarity of geometric shapes.

4.  Standard notation for an equivalence relation.

5.  In probability and statistics, may specify the probability distribution of a random variable. For example, $X\sim N(0,1)$ means that the distribution of the random variable X is standard normal.

6.  Notation for showing proportionality. See also ∝ for a less ambiguous symbol.

≡

1.  Denotes an identity, that is, an equality that is true whichever values are given to the variables occurring in it.

2.  In number theory, and more specifically in modular arithmetic, denotes the congruence modulo an integer.

$\cong$

1.  May denote an isomorphism between two mathematical structures, and is read as "is isomorphic to".

2.  In geometry, may denote the congruence of two geometric shapes (that is the equality up to a displacement), and is read "is congruent to".

Comparison

<

1.  Strict inequality between two numbers; means and is read as "less than".

2.  Commonly used for denoting any strict order.

3.  Between two groups, may mean that the first one is a proper subgroup of the second one.

>

1.  Strict inequality between two numbers; means and is read as "greater than".

2.  Commonly used for denoting any strict order.

3.  Between two groups, may mean that the second one is a proper subgroup of the first one.

≤

1.  Means "less than or equal to". That is, whatever A and B are, A ≤ B is equivalent to A < B or A = B.

2.  Between two groups, may mean that the first one is a subgroup of the second one.

≥

1.  Means "greater than or equal to". That is, whatever A and B are, A ≥ B is equivalent to A > B or A = B.

2.  Between two groups, may mean that the second one is a subgroup of the first one.

≪ , ≫

1.  Means "much less than" and "much greater than". Generally, much is not formally defined, but means that the lesser quantity can be neglected with respect to the other. This is generally the case when the lesser quantity is smaller than the other by one or several orders of magnitude.

2.  In measure theory, $\mu \ll \nu$ means that the measure $\mu$ is absolutely continuous with respect to the measure $\nu$.

≦

1.  A rarely used symbol, generally used as a synonym of ≤.

≺ , ≻

1.  Often used for denoting an order or, more generally, a preorder, when it would be confusing or not convenient to use < and >.

2.  Sequention in asynchronous logic.

Set theory

∅

Denotes the empty set, and is more often written $\emptyset$. Using set-builder notation, it may also be denoted $\{\}$.

#

1.  Number of elements: $\#{}S$ may denote the cardinality of the set S. An alternative notation is $|S|$; see $|\square |$.

2.  Primorial: $n{}\#$ denotes the product of the prime numbers that are not greater than n.

3.  In topology, $M\#N$ denotes the connected sum of two manifolds or two knots.

∈

Denotes set membership, and is read "in" or "belongs to". That is, $x\in S$ means that x is an element of the set S.

∉

Means "not in". That is, $x\notin S$ means $\neg (x\in S)$.

⊂

Denotes set inclusion. However two slightly different definitions are common.

1.  $A\subset B$ may mean that A is a subset of B, and is possibly equal to B; that is, every element of A belongs to B; in formula, $\forall {}x,\,x\in A\Rightarrow x\in B$.

2.  $A\subset B$ may mean that A is a proper subset of B, that is the two sets are different, and every element of A belongs to B; in formula, $A\neq B\land \forall {}x,\,x\in A\Rightarrow x\in B$.

⊆

$A\subseteq B$ means that A is a subset of B. Used for emphasizing that equality is possible, or when the second definition of $A\subset B$ is used.

⊊

$A\subsetneq B$ means that A is a proper subset of B. Used for emphasizing that $A\neq B$, or when the first definition of $A\subset B$ is used.

⊃, ⊇, ⊋

Denote the converse relation of $\subset$, $\subseteq$, and $\subsetneq$ respectively. For example, $B\supset A$ is equivalent to $A\subset B$.

∪

Denotes set-theoretic union, that is, $A\cup B$ is the set formed by the elements of A and B together. That is, $A\cup B=\{x\mid (x\in A)\lor (x\in B)\}$.

∩

Denotes set-theoretic intersection, that is, $A\cap B$ is the set formed by the elements of both A and B. That is, $A\cap B=\{x\mid (x\in A)\land (x\in B)\}$.

∖

Set difference; that is, $A\setminus B$ is the set formed by the elements of A that are not in B. Sometimes, $A-B$ is used instead; see – in § Arithmetic operators.

⊖ or $\triangle$

Symmetric difference: that is, $A\ominus B$ or $A\operatorname {\triangle } B$ is the set formed by the elements that belong to exactly one of the two sets A and B.

∁

1.  With a subscript, denotes a set complement: that is, if $B\subseteq A$, then $\complement _{A}B=A\setminus B$.

2.  Without a subscript, denotes the absolute complement; that is, $\complement A=\complement _{U}A$, where U is a set implicitly defined by the context, which contains all sets under consideration. This set U is sometimes called the universe of discourse.

×

See also × in § Arithmetic operators.

1.  Denotes the Cartesian product of two sets. That is, $A\times B$ is the set formed by all pairs of an element of A and an element of B.

2.  Denotes the direct product of two mathematical structures of the same type, which is the Cartesian product of the underlying sets, equipped with a structure of the same type. For example, direct product of rings, direct product of topological spaces.

3.  In category theory, denotes the direct product (often called simply product) of two objects, which is a generalization of the preceding concepts of product.

⊔

Denotes the disjoint union. That is, if A and B are sets then $A\sqcup B=\left(A\times \{i_{A}\}\right)\cup \left(B\times \{i_{B}\}\right)$ is a set of pairs where i_A and i_B are distinct indices discriminating the members of A and B in $A\sqcup B$.

∐

1.  An alternative to $\sqcup$.

2.  Denotes the coproduct of mathematical structures or of objects in a category.

Basic logic

Several logical symbols are widely used in all mathematics, and are listed here. For symbols that are used only in mathematical logic, or are rarely used, see List of logic symbols.

¬

Denotes logical negation, and is read as "not". If E is a logical predicate, $\neg E$ is the predicate that evaluates to true if and only if E evaluates to false. For clarity, it is often replaced by the word "not". In programming languages and some mathematical texts, it is sometimes replaced by "~" or "!", which are easier to type on some keyboards.

∨

1.  Denotes the logical or, and is read as "or". If E and F are logical predicates, $E\lor F$ is true if either E, F, or both are true. It is often replaced by the word "or".

2.  In lattice theory, denotes the join or least upper bound operation.

3.  In topology, denotes the wedge sum of two pointed spaces.

∧

1.  Denotes the logical and, and is read as "and". If E and F are logical predicates, $E\land F$ is true if E and F are both true. It is often replaced by the word "and" or the symbol "&".

2.  In lattice theory, denotes the meet or greatest lower bound operation.

3.  In multilinear algebra, geometry, and multivariable calculus, denotes the wedge product or the exterior product.

⊻

Exclusive or: if E and F are two Boolean variables or predicates, $E\veebar F$ denotes the exclusive or. Notations E XOR F and $E\oplus F$ are also commonly used; see ⊕.

∀

1.  Denotes universal quantification and is read as "for all". If E is a logical predicate, $\forall xE$ means that E is true for all possible values of the variable x.

2.  Often used improperly in plain text as an abbreviation of "for all" or "for every".

∃

1.  Denotes existential quantification and is read "there exists ... such that". If E is a logical predicate, $\exists xE$ means that there exists at least one value of x for which E is true.

2.  Often used improperly in plain text as an abbreviation of "there exists".

∃!

Denotes uniqueness quantification, that is, $\exists !xP$ means "there exists exactly one x such that P (is true)". In other words, $\exists !xP(x)$ is an abbreviation of $\exists x\,(P(x)\,\wedge \neg \exists y\,(P(y)\wedge y\neq x))$.

⇒

1.  Denotes material conditional, and is read as "implies". If P and Q are logical predicates, $P\Rightarrow Q$ means that if P is true, then Q is also true. Thus, $P\Rightarrow Q$ is logically equivalent with $Q\lor \neg P$.

2.  Often used improperly in plain text as an abbreviation of "implies".

⇔

1.  Denotes logical equivalence, and is read "is equivalent to" or "if and only if". If P and Q are logical predicates, $P\Leftrightarrow Q$ is thus an abbreviation of $(P\Rightarrow Q)\land (Q\Rightarrow P)$, or of $(P\land Q)\lor (\neg P\land \neg Q)$.

2.  Often used improperly in plain text as an abbreviation of "if and only if".

⊤

1.  $\top$ denotes the logical predicate always true.

2.  Denotes also the truth value true.

3.  Sometimes denotes the top element of a bounded lattice (previous meanings are specific examples).

4.  For the use as a superscript, see □^⊤.

⊥

1.  $\bot$ denotes the logical predicate always false.

2.  Denotes also the truth value false.

3.  Sometimes denotes the bottom element of a bounded lattice (previous meanings are specific examples).

4.  In Cryptography often denotes an error in place of a regular value.

5.  For the use as a superscript, see □^⊥.

6.  For the similar symbol, see $\perp$.

Blackboard bold

The blackboard bold typeface is widely used for denoting the basic number systems. These systems are often also denoted by the corresponding uppercase bold letter. A clear advantage of blackboard bold is that these symbols cannot be confused with anything else. This allows using them in any area of mathematics, without having to recall their definition. For example, if one encounters $\mathbb {R}$ in combinatorics, one should immediately know that this denotes the real numbers, although combinatorics does not study the real numbers (but it uses them for many proofs).

$\mathbb {N}$

Denotes the set of natural numbers $\{1,2,\ldots \}$, or sometimes $\{0,1,2,\ldots \}$. It is often denoted also by $\mathbf {N}$. When the distinction is important and readers might assume either definition, $\mathbb {N} _{1}$ and $\mathbb {N} _{0}$ are used, respectively, to denote one of them unambiguously.

$\mathbb {Z}$

Denotes the set of integers $\{\ldots ,-2,-1,0,1,2,\ldots \}$. It is often denoted also by $\mathbf {Z}$.

$\mathbb {Z} _{p}$

1.  Denotes the set of p-adic integers, where p is a prime number.

2.  Sometimes, $\mathbb {Z} _{n}$ denotes the integers modulo n, where n is an integer greater than 0. The notation $\mathbb {Z} /n\mathbb {Z}$ is also used, and is less ambiguous.

$\mathbb {Q}$

Denotes the set of rational numbers (fractions of two integers). It is often denoted also by $\mathbf {Q}$.

$\mathbb {Q} _{p}$

Denotes the set of p-adic numbers, where p is a prime number.

$\mathbb {R}$

Denotes the set of real numbers. It is often denoted also by $\mathbf {R}$.

$\mathbb {C}$

Denotes the set of complex numbers. It is often denoted also by $\mathbf {C}$.

$\mathbb {H}$

Denotes the set of quaternions. It is often denoted also by $\mathbf {H}$.

$\mathbb {F} _{q}$

Denotes the finite field with q elements, where q is a prime power (including prime numbers). It is denoted also by GF(q).

$\mathbb {O}$

Used on rare occasions to denote the set of octonions. It is often denoted also by $\mathbf {O}$.

Calculus

□'

Lagrange's notation for the derivative: If f is a function of a single variable, $f'$, read as "f prime", is the derivative of f with respect to this variable. The second derivative is the derivative of $f'$, and is denoted $f''$.

${\dot {\Box }}$

Newton's notation, most commonly used for the derivative with respect to time: If x is a variable depending on time, then ${\dot {x}}$ is its derivative with respect to time. In particular, if x represents a moving point, then ${\dot {x}}$ is its velocity.

${\ddot {\Box }}$

Newton's notation, for the second derivative: If x is a variable that represents a moving point, then ${\ddot {x}}$ is its acceleration.

d □d □

Leibniz's notation for the derivative, which is used in several slightly different ways.

1.  If y is a variable that depends on x, then $\textstyle {\frac {\mathrm {d} y}{\mathrm {d} x}}$, read as "d y over d x", is the derivative of y with respect to x.

2.  If f is a function of a single variable x, then $\textstyle {\frac {\mathrm {d} f}{\mathrm {d} x}}$ is the derivative of f, and $\textstyle {\frac {\mathrm {d} f}{\mathrm {d} x}}(a)$ is the value of the derivative at a.

3.  Total derivative: If $f(x_{1},\ldots ,x_{n})$ is a function of several variables that depend on x, then $\textstyle {\frac {\mathrm {d} f}{\mathrm {d} x}}$ is the derivative of f considered as a function of x. That is, $\textstyle {\frac {\mathrm {d} f}{dx}}=\sum _{i=1}^{n}{\frac {\partial f}{\partial x_{i}}}\,{\frac {\mathrm {d} x_{i}}{\mathrm {d} x}}$.

∂ □∂ □

Partial derivative: If $f(x_{1},\ldots ,x_{n})$ is a function of several variables, $\textstyle {\frac {\partial f}{\partial x_{i}}}$ is the derivative with respect to the ith variable considered as an independent variable, the other variables being considered as constants.

𝛿 □𝛿 □

Functional derivative: If $f(y_{1},\ldots ,y_{n})$ is a functional of several functions, $\textstyle {\frac {\delta f}{\delta y_{i}}}$ is the functional derivative with respect to the nth function considered as an independent variable, the other functions being considered constant.

${\overline {\Box }}$

1.  Complex conjugate: If z is a complex number, then ${\overline {z}}$ is its complex conjugate. For example, ${\overline {a+bi}}=a-bi$.

2.  Topological closure: If S is a subset of a topological space T, then ${\overline {S}}$ is its topological closure, that is, the smallest closed subset of T that contains S.

3.  Algebraic closure: If F is a field, then ${\overline {F}}$ is its algebraic closure, that is, the smallest algebraically closed field that contains F. For example, ${\overline {\mathbb {Q} }}$ is the field of all algebraic numbers.

4.  Mean value: If x is a variable that takes its values in some sequence of numbers S, then ${\overline {x}}$ may denote the mean of the elements of S.

→

1.  $A\to B$ denotes a function with domain A and codomain B. For naming such a function, one writes $f:A\to B$, which is read as "f from A to B".

2.  More generally, $A\to B$ denotes a homomorphism or a morphism from A to B.

3.  May denote a logical implication. For the material implication that is widely used in mathematics reasoning, it is nowadays generally replaced by ⇒. In mathematical logic, it remains used for denoting implication, but its exact meaning depends on the specific theory that is studied.

4.  Over a variable name, means that the variable represents a vector, in a context where ordinary variables represent scalars; for example, ${\overrightarrow {v}}$. Boldface ($\mathbf {v}$) or a circumflex (${\hat {v}}$) are often used for the same purpose.

5.  In Euclidean geometry and more generally in affine geometry, ${\overrightarrow {PQ}}$ denotes the vector defined by the two points P and Q, which can be identified with the translation that maps P to Q. The same vector can be denoted also $Q-P$; see Affine space.

↦

Used for defining a function without having to name it. For example, $x\mapsto x^{2}$ is the square function.

○

1.  Function composition: If f and g are two functions, then $g\circ f$ is the function such that $(g\circ f)(x)=g(f(x))$ for every value of x.

2.  Hadamard product of matrices: If A and B are two matrices of the same size, then $A\circ B$ is the matrix such that $(A\circ B)_{i,j}=(A)_{i,j}(B)_{i,j}$. Possibly, $\circ$ is also used instead of ⊙ for the Hadamard product of power series.

∂

1.  Boundary of a topological subspace: If S is a subspace of a topological space, then its boundary, denoted $\partial S$, is the set difference between the closure and the interior of S.

2.  Partial derivative: see ∂□∂□.

∫

1.  Without a subscript, denotes an antiderivative. For example, $\textstyle \int x^{2}dx={\frac {x^{3}}{3}}+C$.

2.  With a subscript and a superscript, or expressions placed below and above it, denotes a definite integral. For example, $\textstyle \int _{a}^{b}x^{2}dx={\frac {b^{3}-a^{3}}{3}}$.

3.  With a subscript that denotes a curve, denotes a line integral. For example, $\textstyle \int _{C}f=\int _{a}^{b}f(r(t))r'(t)\operatorname {d} t$, if r is a parametrization of the curve C, from a to b.

∮

Often used, typically in physics, instead of $\textstyle \int$ for line integrals over a closed curve.

∬, ∯

Similar to $\textstyle \int$ and $\textstyle \oint$ for surface integrals.

${\boldsymbol {\nabla }}$ or ${\vec {\nabla }}$

Nabla, the gradient or vector derivative operator $\textstyle \left({\frac {\partial }{\partial x}},{\frac {\partial }{\partial y}},{\frac {\partial }{\partial z}}\right)$, also called del or grad.

∇² or ∇⋅∇

Laplace operator or Laplacian: $\textstyle {\frac {\partial ^{2}}{\partial x^{2}}}+{\frac {\partial ^{2}}{\partial y^{2}}}+{\frac {\partial ^{2}}{\partial z^{2}}}$. The forms $\nabla ^{2}$ and ${\boldsymbol {\nabla }}\cdot {\boldsymbol {\nabla }}$ represent the dot product of the gradient (${\boldsymbol {\nabla }}$ or ${\vec {\nabla }}$) with itself. Also notated Δ (next item).

Δ

(Capital Greek letter delta—not to be confused with $\triangle$, which may denote a geometric triangle or, alternatively, the symmetric difference of two sets.}}

1.  Another notation for the Laplacian (see above).

2.  Operator of finite difference.

${\boldsymbol {\partial }}$ or $\partial _{\mu }$

(Note: the notation $\Box$ is not recommended for the four-gradient since both $\Box$ and ${\Box }^{2}$ are used to denote the d'Alembertian; see below.)

Quad, the 4-vector gradient operator or four-gradient, $\textstyle \left({\frac {\partial }{\partial t}},{\frac {\partial }{\partial x}},{\frac {\partial }{\partial y}},{\frac {\partial }{\partial z}}\right)$.

$\Box$ or ${\Box }^{2}$

(here an actual box, not a placeholder)

Denotes the d'Alembertian or squared four-gradient, which is a generalization of the Laplacian to four-dimensional spacetime. In flat spacetime with Euclidean coordinates, this may mean either $~\textstyle -{\frac {\partial ^{2}}{\partial t^{2}}}+{\frac {\partial ^{2}}{\partial x^{2}}}+{\frac {\partial ^{2}}{\partial y^{2}}}+{\frac {\partial ^{2}}{\partial z^{2}}}~\;$ or $\;~\textstyle +{\frac {\partial ^{2}}{\partial t^{2}}}-{\frac {\partial ^{2}}{\partial x^{2}}}-{\frac {\partial ^{2}}{\partial y^{2}}}-{\frac {\partial ^{2}}{\partial z^{2}}}~\;$; the sign convention must be specified. In curved spacetime (or flat spacetime with non-Euclidean coordinates), the definition is more complicated. Also called box or quabla.

Linear and multilinear algebra

∑ (Sigma notation)

1.  Denotes the sum of a finite number of terms, which are determined by subscripts and superscripts (which can also be placed below and above), such as in $\textstyle \sum _{i=1}^{n}i^{2}$ or $\textstyle \sum _{0<i<j<n}j-i$.

2.  Denotes a series and, if the series is convergent, the sum of the series. For example, $\textstyle \sum _{i=0}^{\infty }{\frac {x^{i}}{i!}}=e^{x}$.

∏ (Capital-pi notation)

1.  Denotes the product of a finite number of terms, which are determined by subscripts and superscripts (which can also be placed below and above), such as in $\textstyle \prod _{i=1}^{n}i^{2}$ or $\textstyle \prod _{0<i<j<n}j-i$.

2.  Denotes an infinite product. For example, the Euler product formula for the Riemann zeta function is $\textstyle \zeta (z)=\prod _{n=1}^{\infty }{\frac {1}{1-p_{n}^{-z}}}$.

3.  Also used for the Cartesian product of any number of sets and the direct product of any number of mathematical structures.

⊕

1.  Internal direct sum: if E and F are abelian subgroups of an abelian group V, notation $V=E\oplus F$ means that V is the direct sum of E and F; that is, every element of V can be written in a unique way as the sum of an element of E and an element of F. This applies also when E and F are linear subspaces or submodules of the vector space or module V.

2.  Direct sum: if E and F are two abelian groups, vector spaces, or modules, then their direct sum, denoted $E\oplus F$ is an abelian group, vector space, or module (respectively) equipped with two monomorphisms $f:E\to E\oplus F$ and $g:F\to E\oplus F$ such that $E\oplus F$ is the internal direct sum of $f(E)$ and $g(F)$. This definition makes sense because this direct sum is unique up to a unique isomorphism.

3.  Exclusive or: if E and F are two Boolean variables or predicates, $E\oplus F$ may denote the exclusive or. Notations E XOR F and $E\veebar F$ are also commonly used; see ⊻.

⊗

Denotes the tensor product. If E and F are abelian groups, vector spaces, or modules over a commutative ring, then the tensor product of E and F, denoted $E\otimes F$ is an abelian group, a vector space or a module (respectively), equipped with a bilinear map $(e,f)\mapsto e\otimes f$ from $E\times F$ to $E\otimes F$, such that the bilinear maps from $E\times F$ to any abelian group, vector space or module G can be identified with the linear maps from $E\otimes F$ to G. If E and F are vector spaces over a field R, or modules over a ring R, the tensor product is often denoted $E\otimes _{R}F$ to avoid ambiguity.

□^⊤

1.  Transpose: if A is a matrix, $A^{\top }$ denotes the transpose of A, that is, the matrix obtained by exchanging rows and columns of A. Notation $^{\top }\!\!A$ is also used. The symbol $\top$ is often replaced by the letter T or t.

2.  For inline uses of the symbol, see ⊤.

□^⊥

1.  Orthogonal complement: If W is a linear subspace of an inner product space V, then $W^{\bot }$ denotes its orthogonal complement, that is, the linear space of the elements of V whose inner products with the elements of W are all zero.

2.  Orthogonal subspace in the dual space: If W is a linear subspace (or a submodule) of a vector space (or of a module) V, then $W^{\bot }$ may denote the orthogonal subspace of W, that is, the set of all linear forms that map W to zero.

3.  For inline uses of the symbol, see ⊥.

Advanced group theory

⋉
⋊

1.  Inner semidirect product: if N and H are subgroups of a group G, such that N is a normal subgroup of G, then $G=N\rtimes H$ and $G=H\ltimes N$ mean that G is the semidirect product of N and H, that is, that every element of G can be uniquely decomposed as the product of an element of N and an element of H. (Unlike for the direct product of groups, the element of H may change if the order of the factors is changed.)

2.  Outer semidirect product: if N and H are two groups, and $\varphi$ is a group homomorphism from N to the automorphism group of H, then $N\rtimes _{\varphi }H=H\ltimes _{\varphi }N$ denotes a group G, unique up to a group isomorphism, which is a semidirect product of N and H, with the commutation of elements of N and H defined by $\varphi$.

≀

In group theory, $G\wr H$ denotes the wreath product of the groups G and H. It is also denoted as $G\operatorname {wr} H$ or $G\operatorname {Wr} H$; see Wreath product § Notation and conventions for several notation variants.

Infinite numbers

∞

1.  The symbol is read as infinity. As an upper bound of a summation, an infinite product, an integral, etc., means that the computation is unlimited. Similarly, $-\infty$ in a lower bound means that the computation is not limited toward negative values.

2.  $-\infty$ and $+\infty$ are the generalized numbers that are added to the real line to form the extended real line.

3.  $\infty$ is the generalized number that is added to the real line to form the projectively extended real line.

𝔠

${\mathfrak {c}}$ denotes the cardinality of the continuum, which is the cardinality of the set of real numbers.

ℵ

With an ordinal i as a subscript, denotes the ith aleph number, that is the ith infinite cardinal. For example, $\aleph _{0}$ is the smallest infinite cardinal, that is, the cardinal of the natural numbers.

ℶ

With an ordinal i as a subscript, denotes the ith beth number. For example, $\beth _{0}$ is the cardinal of the natural numbers, and $\beth _{1}$ is the cardinal of the continuum.

ω

1.  Denotes the first limit ordinal. It is also denoted $\omega _{0}$ and can be identified with the ordered set of the natural numbers.

2.  With an ordinal i as a subscript, denotes the ith limit ordinal that has a cardinality greater than that of all preceding ordinals.

3.  In computer science, denotes the (unknown) greatest lower bound for the exponent of the computational complexity of matrix multiplication.

4.  Written as a function of another function, it is used for comparing the asymptotic growth of two functions. See Big O notation § Related asymptotic notations.

5.  In number theory, may denote the prime omega function. That is, $\omega (n)$ is the number of distinct prime factors of the integer n.

Brackets

Many sorts of brackets are used in mathematics. Their meanings depend not only on their shapes, but also on the nature and the arrangement of what is delimited by them, and sometimes what appears between or before them. For this reason, in the entry titles, the symbol □ is used as a placeholder for schematizing the syntax that underlies the meaning.

Parentheses

(□)

Used in an expression for specifying that the sub-expression between the parentheses has to be considered as a single entity; typically used for specifying the order of operations.

□(□)
□(□, □)
□(□, ..., □)

1.  Functional notation: if the first $\Box$ is the name (symbol) of a function, denotes the value of the function applied to the expression between the parentheses; for example, $f(x)$, $\sin(x+y)$. In the case of a multivariate function, the parentheses contain several expressions separated by commas, such as $f(x,y)$.

2.  May also denote a product, such as in $a(b+c)$. When the confusion is possible, the context must distinguish which symbols denote functions, and which ones denote variables.

(□, □)

1.  Denotes an ordered pair of mathematical objects, for example, $(\pi ,0)$.

2.  If a and b are real numbers, $-\infty$, or $+\infty$, and a < b, then $(a,b)$ denotes the open interval delimited by a and b. See ]□, □[ for an alternative notation.

3.  If a and b are integers, $(a,b)$ may denote the greatest common divisor of a and b. Notation $\gcd(a,b)$ is often used instead.

(□, □, □)

If x, y, z are vectors in $\mathbb {R} ^{3}$, then $(x,y,z)$ may denote the scalar triple product. See also [□,□,□] in § Square brackets.

(□, ..., □)

Denotes a tuple. If there are n objects separated by commas, it is an n-tuple.

(□, □, ...)
(□, ..., □, ...)

Denotes an infinite sequence.

${\begin{pmatrix}\Box &\cdots &\Box \\\vdots &\ddots &\vdots \\\Box &\cdots &\Box \end{pmatrix}}$

Denotes a matrix. Often denoted with square brackets.

${\binom {\Box }{\Box }}$

Denotes a binomial coefficient: Given two nonnegative integers, ${\binom {n}{k}}$ is read as "n choose k", and is defined as the integer ${\frac {n(n-1)\cdots (n-k+1)}{1\cdot 2\cdots k}}={\frac {n!}{k!\,(n-k)!}}$ (if k = 0, its value is conventionally 1). Using the left-hand-side expression, it denotes a polynomial in n, and is thus defined and used for any real or complex value of n.

(□□)

Legendre symbol: If p is an odd prime number and a is an integer, the value of $\left({\frac {a}{p}}\right)$ is 1 if a is a quadratic residue modulo p; it is –1 if a is a quadratic non-residue modulo p; it is 0 if p divides a. The same notation is used for the Jacobi symbol and Kronecker symbol, which are generalizations where p is respectively any odd positive integer, or any integer.

Square brackets

[□]

1.  Sometimes used as a synonym of (□) for avoiding nested parentheses.

2.  Equivalence class: given an equivalence relation, $[x]$ often denotes the equivalence class of the element x.

3.  Integral part: if x is a real number, $[x]$ often denotes the integral part or truncation of x, that is, the integer obtained by removing all digits after the decimal mark. This notation has also been used for other variants of floor and ceiling functions.

4.  Iverson bracket: if P is a predicate, $[P]$ may denote the Iverson bracket, that is the function that takes the value 1 for the values of the free variables in P for which P is true, and takes the value 0 otherwise. For example, $[x=y]$ is the Kronecker delta function, which equals one if $x=y$, and zero otherwise.

□[□]

Image of a subset: if S is a subset of the domain of the function f, then $f[S]$ is sometimes used for denoting the image of S. When no confusion is possible, notation f(S) is commonly used.

[□, □]

1.  Closed interval: if a and b are real numbers such that $a\leq b$, then $[a,b]$ denotes the closed interval defined by them.

2.  Commutator (group theory): if a and b belong to a group, then $[a,b]=a^{-1}b^{-1}ab$.

3.  Commutator (ring theory): if a and b belong to a ring, then $[a,b]=ab-ba$.

4.  Denotes the Lie bracket, the operation of a Lie algebra.

[□ : □]

1.  Degree of a field extension: if F is an extension of a field E, then $[F:E]$ denotes the degree of the field extension $F/E$. For example, $[\mathbb {C} :\mathbb {R} ]=2$.

2.  Index of a subgroup: if H is a subgroup of a group E, then $[G:H]$ denotes the index of H in G. The notation |G:H| is also used

[□, □, □]

If x, y, z are vectors in $\mathbb {R} ^{3}$, then $[x,y,z]$ may denote the scalar triple product. See also (□,□,□) in § Parentheses.

${\begin{bmatrix}\Box &\cdots &\Box \\\vdots &\ddots &\vdots \\\Box &\cdots &\Box \end{bmatrix}}$

Denotes a matrix. Often denoted with parentheses.

Braces

( }

Set-builder notation for the empty set, also denoted $\emptyset$ or ∅.

{□}

1.  Sometimes used as a synonym of (□) and [□] for avoiding nested parentheses.

2.  Set-builder notation for a singleton set: $\{x\}$ denotes the set that has x as a single element.

{□, ..., □}

Set-builder notation: denotes the set whose elements are listed between the braces, separated by commas.

{□ : □}
{□ | □}

Set-builder notation: if $P(x)$ is a predicate depending on a variable x, then both $\{x:P(x)\}$ and $\{x\mid P(x)\}$ denote the set formed by the values of x for which $P(x)$ is true.

Single brace

1.  Used for emphasizing that several equations have to be considered as simultaneous equations; for example, $\textstyle {\begin{cases}2x+y=1\\3x-y=1\end{cases}}$.

2.  Piecewise definition; for example, $\textstyle |x|={\begin{cases}x&{\text{if }}x\geq 0\\-x&{\text{if }}x<0\end{cases}}$.

3.  Used for grouped annotation of elements in a formula; for example, $\textstyle \underbrace {(a,b,\ldots ,z)} _{26}$, $\textstyle \overbrace {1+2+\cdots +100} ^{=5050}$, $\textstyle \left.{\begin{bmatrix}A\\B\end{bmatrix}}\right\}m+n{\text{ rows}}$

Other brackets

|□|

1.  Absolute value: if x is a real or complex number, $|x|$ denotes its absolute value.

2.  Number of elements: If S is a set, $|x|$ may denote its cardinality, that is, its number of elements. $\#S$ is also often used, see #.

3.  Length of a line segment: If P and Q are two points in a Euclidean space, then $|PQ|$ often denotes the length of the line segment that they define, which is the distance from P to Q, and is often denoted $d(P,Q)$.

4.  For a similar-looking operator, see |.

|□:□|

Index of a subgroup: if H is a subgroup of a group G, then $|G:H|$ denotes the index of H in G. The notation [G:H] is also used

$\textstyle {\begin{vmatrix}\Box &\cdots &\Box \\\vdots &\ddots &\vdots \\\Box &\cdots &\Box \end{vmatrix}}$

${\begin{vmatrix}x_{1,1}&\cdots &x_{1,n}\\\vdots &\ddots &\vdots \\x_{n,1}&\cdots &x_{n,n}\end{vmatrix}}$ denotes the determinant of the square matrix ${\begin{bmatrix}x_{1,1}&\cdots &x_{1,n}\\\vdots &\ddots &\vdots \\x_{n,1}&\cdots &x_{n,n}\end{bmatrix}}$.

||□||

1.  Denotes the norm of an element of a normed vector space.

2.  For the similar-looking operator named parallel, see ∥.

⌊□⌋

Floor function: if x is a real number, $\lfloor x\rfloor$ is the greatest integer that is not greater than x.

⌈□⌉

Ceiling function: if x is a real number, $\lceil x\rceil$ is the lowest integer that is not lesser than x.

⌊□⌉

Nearest integer function: if x is a real number, $\lfloor x\rceil$ is the integer that is the closest to x.

]□, □[

Open interval: If a and b are real numbers, $-\infty$, or $+\infty$, and $a<b$, then $]a,b[$ denotes the open interval delimited by a and b. See (□, □) for an alternative notation.

(□, □]
]□, □]

Both notations are used for a left-open interval.

[□, □)
[□, □[

Both notations are used for a right-open interval.

⟨□⟩

1.  Generated object: if S is a set of elements in an algebraic structure, $\langle S\rangle$ denotes often the object generated by S. If $S=\{s_{1},\ldots ,s_{n}\}$, one writes $\langle s_{1},\ldots ,s_{n}\rangle$ (that is, braces are omitted). In particular, this may denote

• the linear span in a vector space (also often denoted Span(S)),
• the generated subgroup in a group,
• the generated ideal in a ring,
• the generated submodule in a module.

2.  Often used, mainly in physics, for denoting an expected value. In probability theory, $E(X)$ is generally used instead of $\langle S\rangle$.

⟨□, □⟩
⟨□ | □⟩

Both $\langle x,y\rangle$ and $\langle x\mid y\rangle$ are commonly used for denoting the inner product in an inner product space.

⟨□| and |□⟩

Bra–ket notation or Dirac notation: if x and y are elements of an inner product space, $|x\rangle$ is the vector defined by x, and $\langle y|$ is the covector defined by y; their inner product is $\langle y\mid x\rangle$.

Symbols that do not belong to formulas

In this section, the symbols that are listed are used as some sorts of punctuation marks in mathematical reasoning, or as abbreviations of natural language phrases. They are generally not used inside a formula. Some were used in classical logic for indicating the logical dependence between sentences written in plain language. Except for the first two, they are normally not used in printed mathematical texts since, for readability, it is generally recommended to have at least one word between two formulas. However, they are still used on a black board for indicating relationships between formulas.

■ , □

Used for marking the end of a proof and separating it from the current text. The initialism Q.E.D. or QED (bahasa Latin: quod erat demonstrandum, "as was to be shown") is often used for the same purpose, either in its upper-case form or in lower case.

☡

Bourbaki dangerous bend symbol: Sometimes used in the margin to forewarn readers against serious errors, where they risk falling, or to mark a passage that is tricky on a first reading because of an especially subtle argument.

∴

Abbreviation of "therefore". Placed between two assertions, it means that the first one implies the second one. For example: "All humans are mortal, and Socrates is a human. ∴ Socrates is mortal."

∵

Abbreviation of "because" or "since". Placed between two assertions, it means that the first one is implied by the second one. For example: "11 is prime ∵ it has no positive integer factors other than itself and one."

∋

1.  Abbreviation of "such that". For example, $x\ni x>3$ is normally printed "x such that $x>3$".

2.  Sometimes used for reversing the operands of $\in$; that is, $S\ni x$ has the same meaning as $x\in S$. See ∈ in § Set theory.

∝

Abbreviation of "is proportional to".

Miscellaneous

!

1.  Factorial: if n is a positive integer, n! is the product of the first n positive integers, and is read as "n factorial".

2.  Subfactorial: if n is a positive integer, !n is the number of derangements of a set of n elements, and is read as "the subfactorial of n".

*

Many different uses in mathematics; see Asterisk § Mathematics.

|

1.  Divisibility: if m and n are two integers, $m\mid n$ means that m divides n evenly.

2.  In set-builder notation, it is used as a separator meaning "such that"; see (□ | □}.

3.  Restriction of a function: if f is a function, and S is a subset of its domain, then $f|_{S}$ is the function with S as a domain that equals f on S.

4.  Conditional probability: $P(X\mid E)$ denotes the probability of X given that the event E occurs. Also denoted $P(X/E)$; see "/".

5.  For several uses as brackets (in pairs or with ⟨ and ⟩) see § Other brackets.

∤

Non-divisibility: $n\nmid m$ means that n is not a divisor of m.

∥

1.  Denotes parallelism in elementary geometry: if PQ and RS are two lines, $PQ\parallel RS$ means that they are parallel.

2.  Parallel, an arithmetical operation used in electrical engineering for modeling parallel resistors: $x\parallel y={\frac {1}{{\frac {1}{x}}+{\frac {1}{y}}}}$.

3.  Used in pairs as brackets, denotes a norm; see ||□||.

∦

Sometimes used for denoting that two lines are not parallel; for example, $PQ\not \parallel RS$.

$\perp$

1.  Denotes perpendicularity and orthogonality. For example, if A, B, C are three points in a Euclidean space, then $AB\perp AC$ means that the line segments AB and AC are perpendicular, and form a right angle.

2.  For the similar symbol, see $\bot$.

⊙

Hadamard product of power series: if $\textstyle S=\sum _{i=0}^{\infty }s_{i}x^{i}$ and $\textstyle T=\sum _{i=0}^{\infty }t_{i}x^{i}$, then $\textstyle S\odot T=\sum _{i=0}^{\infty }s_{i}t_{i}x^{i}$. Possibly, $\odot$ is also used instead of ○ for the Hadamard product of matrices.

See also

Related articles

• Language of mathematics
• Mathematical notation
• Notation in probability and statistics
• Physical constants

Related lists

• List of mathematical symbols by subject
• List of logic symbols
• List of mathematical constants
• Table of mathematical symbols by introduction date
• Blackboard bold
• Greek letters used in mathematics, science, and engineering
• List of mathematical uses of Latin letters
• List of common physics notations
• List of letters used in mathematics and science
• List of mathematical abbreviations
• List of typographical symbols and punctuation marks
• ISO 31-11 (Mathematical signs and symbols for use in physical sciences and technology)
• List of APL functions

Unicode symbols

• Unicode block
• Mathematical Alphanumeric Symbols (Unicode block)
• List of Unicode characters
• Letterlike Symbols
• Mathematical operators and symbols in Unicode
• Miscellaneous Mathematical Symbols: A, B, Technical
• Arrow (symbol) and Miscellaneous Symbols and Arrows
• Number Forms
• Geometric Shapes

External links

• Jeff Miller: Earliest Uses of Various Mathematical Symbols
• Numericana: Scientific Symbols and Icons
• GIF and PNG Images for Math Symbols
• Mathematical Symbols in Unicode
• Detexify: LaTeX Handwriting Recognition Tool

Some Unicode charts of mathematical operators and symbols:

• Index of Unicode symbols
• Range 2100–214F: Unicode Letterlike Symbols
• Range 2190–21FF: Unicode Arrows
• Range 2200–22FF: Unicode Mathematical Operators
• Range 27C0–27EF: Unicode Miscellaneous Mathematical Symbols–A
• Range 2980–29FF: Unicode Miscellaneous Mathematical Symbols–B
• Range 2A00–2AFF: Unicode Supplementary Mathematical Operators

Some Unicode cross-references:

• Short list of commonly used LaTeX symbols and Comprehensive LaTeX Symbol List
• MathML Characters - sorts out Unicode, HTML and MathML/TeX names on one page
• Unicode values and MathML names
• Unicode values and Postscript names from the source code for Ghostscript