This article may require cleanup to meet Wikipedia's quality standards. The specific problem is: For complying with WP:Indiscriminate, WP:NOT#DICT, WP:Notability and several other policies and guidelines, many entries must be removed. More precisely, for being kept, a symbol must be either a standard or widely used in some area(s) of mathematics. For each symbol that is kept, the status must be clear (standard in all mathematics, standard in a specific part of mathematics, possibly ambiguous if used without care, etc.) and references to standard textbooks must be given for verifiability. (September 2019) (Learn how and when to remove this template message) 
This is a list of mathematical symbols used in all branches of mathematics to express a formula or to represent a constant.
A mathematical concept is independent of the symbol chosen to represent it. For many of the symbols below, the symbol is usually synonymous with the corresponding concept (ultimately an arbitrary choice made as a result of the cumulative history of mathematics), but in some situations, a different convention may be used. For example, depending on context, the triple bar "≡" may represent congruence or a definition. However, in mathematical logic, numerical equality is sometimes represented by "≡" instead of "=", with the latter representing equality of wellformed formulas. In short, convention dictates the meaning.
Each symbol is shown both in HTML, whose display depends on the browser's access to an appropriate font installed on the particular device, and typeset as an image using TeX.
This list is organized by symbol type and is intended to facilitate finding an unfamiliar symbol by its visual appearance. For a related list organized by mathematical topic, see List of mathematical symbols by subject. That list also includes LaTeX and HTML markup, and Unicode code points for each symbol (note that this article doesn't have the latter two, but they could certainly be added).
There is a Wikibooks guide for using maths in LaTeX,^{[1]} and a comprehensive LaTeX symbol list.^{[2]} It is also possible to check to see if a Unicode code point is available as a LaTeX command, or vice versa.^{[3]} Also note that where there is no LaTeX command natively available for a particular symbol (although there may be options that require adding packages), the symbol could be added via other options, such as setting the document up to support Unicode,^{[4]} and entering the character in a variety of ways (e.g. copying and pasting, keyboard shortcuts, the \unicode{<insertcodepoint>}
command^{[5]}) as well as other options^{[6]} and extensive additional information.^{[7]}^{[8]}.
Symbol in HTML 
Symbol in TeX 
Name  Explanation  Examples  

Read as  
Category  
plus;
add 
2 + 7 means the sum of 2 and 7.  2 + 7 = 9  
the disjoint union of ... and ...

A_{1} + A_{2} means the disjoint union of sets A_{1} and A_{2}.  A_{1} = {3, 4, 5, 6} ∧ A_{2} = {7, 8, 9, 10} ⇒ A_{1} + A_{2} = {(3, 1), (4, 1), (5, 1), (6, 1), (7, 2), (8, 2), (9, 2), (10, 2)}  
36 − 11 means the subtraction of 11 from 36.  36 − 11 = 25  
negative;
minus; the opposite of 
−3 means the additive inverse of the number 3.  −(−5) = 5  
minus;
without 
A − B means the set that contains all the elements of A that are not in B. (∖ can also be used for settheoretic complement as described below.) 
{1, 2, 4} − {1, 3, 4} = {2}  
\pm 
plus or minus

6 ± 3 means both 6 + 3 and 6 − 3.  The equation x = 5 ± √4, has two solutions, x = 7 and x = 3.  
plus or minus

10 ± 2 or equivalently 10 ± 20% means the range from 10 − 2 to 10 + 2.  If a = 100 ± 1 mm, then a ≥ 99 mm and a ≤ 101 mm.  
\mp 
minus or plus

6 ± (3 ∓ 5) means 6 + (3 − 5) and 6 − (3 + 5).  Used paired with ± to mean the opposite cos(x ± y) = cos(x) cos(y) ∓ sin(x) sin(y).  
\times \cdot 
times;
multiplied by 
3 × 4 or 3 ⋅ 4 means the multiplication of 3 by 4.  7 ⋅ 8 = 56  
dot

u ⋅ v means the dot product of vectors u and v  (1, 2, 5) ⋅ (3, 4, −1) = 6  
cross

u × v means the cross product of vectors u and v  (1, 2, 5) × (3, 4, −1) =
 
placeholder
(silent)

A · means a placeholder for an argument of a function. Indicates the functional nature of an expression without assigning a specific symbol for an argument.   ·   
\div 
divided by;
over 
6 ÷ 3 or 6 ⁄ 3 means the division of 6 by 3.  2 ÷ 4 = 0.5 12 ⁄ 4 = 3  
mod

G / H means the quotient of group G modulo its subgroup H.  {0, a, 2a, b, b + a, b + 2a} / {0, b} = {{0, b}, {a, b + a}, {2a, b + 2a}}  
quotient set
mod

A/~ means the set of all ~ equivalence classes in A.  If we define ~ by x ~ y ⇔ x − y ∈ ℤ, then ℝ/~ = {x + n : n ∈ ℤ, x ∈ [0,1)}.  
\surd \sqrt{x} 
the (principal) square root of

√x means the nonnegative number whose square is x.  √4 = 2  
the (complex) square root of

If z = r exp(iφ) is represented in polar coordinates with −π < φ ≤ π, then √z = √r exp(iφ/2).  √−1 = i  
\sum 
sum over ... from ... to ... of

means .  
\int 
indefinite integral of
 OR  the antiderivative of 
∫^{} _{} f(x) dx means a function whose derivative is f. 

integral from ... to ... of ... with respect to

∫^{b} _{a} f(x) dx means the signed area between the xaxis and the graph of the function f between x = a and x = b. 
∫^{b} _{a} x^{2} dx = b^{3} − a^{3}/3  
line/ path/ curve/ integral of ... along ...

∫^{} _{C} f ds means the integral of f along the curve C, ∫^{b} _{a} f(r(t)) r'(t) dt, where r is a parametrization of C. (If the curve is closed, the symbol ∮^{} _{} may be used instead, as described below.) 

∮^{}
_{} 
\oint 
Contour integral;
closed line integral contour integral of

Similar to the integral, but used to denote a single integration over a closed curve or loop. It is sometimes used in physics texts involving equations regarding Gauss's Law, and while these formulas involve a closed surface integral, the representations describe only the first integration of the volume over the enclosing surface. Instances where the latter requires simultaneous double integration, the symbol ∯^{} _{} would be more appropriate. A third related symbol is the closed volume integral, denoted by the symbol ∰^{} _{}. The contour integral can also frequently be found with a subscript capital letter C, ∮^{} 
If C is a Jordan curve about 0, then ∮^{} _{C} 1/z dz = 2πi.  
...
⋯ ⋮ ⋰ ⋱ 
\ldots \cdots \vdots \ddots 
and so forth
everywhere

Indicates omitted values from a pattern.  1/2 + 1/4 + 1/8 + 1/16 + ⋯ = 1  
\therefore 
therefore;
so; hence everywhere

Sometimes used in proofs before logical consequences.  All humans are mortal. Socrates is a human. ∴ Socrates is mortal.  
\because 
because;
since everywhere

Sometimes used in proofs before reasoning.  11 is prime ∵ it has no positive integer factors other than itself and one.  
factorial

means the product .  
not

The statement !A is true if and only if A is false. A slash placed through another operator is the same as "!" placed in front. (The symbol ! is primarily from computer science. It is avoided in mathematical texts, where the notation ¬A is preferred.) 
!(!A) ⇔ A x ≠ y ⇔ !(x = y)  
\neg 
not

The statement ¬A is true if and only if A is false. A slash placed through another operator is the same as "¬" placed in front. (The symbol ~ has many other uses, so ¬ or the slash notation is preferred. Computer scientists will often use ! but this is avoided in mathematical texts.) 
¬(¬A) ⇔ A x ≠ y ⇔ ¬(x = y)  
\propto 
is proportional to;
varies as everywhere

y ∝ x means that y = kx for some constant k.  if y = 2x, then y ∝ x.  
\infty 
infinity

∞ is an element of the extended number line that is greater than all real numbers; it often occurs in limits.  
■
□ ∎ ▮ ‣ 
\blacksquare \Box \blacktriangleright 
everywhere

Used to mark the end of a proof. (May also be written Q.E.D.) 
Symbol in HTML 
Symbol in TeX 
Name  Explanation  Examples 

Read as  
Category  
is equal to;
equals everywhere

means and represent the same thing or value.  
\ne, \neq 
is not equal to;
does not equal everywhere

means that and do not represent the same thing or value. (The forms !=, /= or <> are generally used in programming languages where ease of typing and use of ASCII text is preferred.) 

\approx 
approximately equal
is approximately equal to
everywhere

x ≈ y means x is approximately equal to y. This may also be written ≃, ≅, ~, ♎ (Libra Symbol), or ≒. 
π ≈ 3.14159  
is isomorphic to

G ≈ H means that group G is isomorphic (structurally identical) to group H. (≅ can also be used for isomorphic, as described below.) 
Q_{8} / C_{2} ≈ V  
\sim 
has distribution

X ~ D, means the random variable X has the probability distribution D.  X ~ N(0,1), the standard normal distribution  
is row equivalent to

A ~ B means that B can be generated by using a series of elementary row operations on A  
same order of magnitude

m ~ n means the quantities m and n have the same order of magnitude, or general size. (Note that ~ is used for an approximation that is poor, otherwise use ≈ .) 
2 ~ 5 8 × 9 ~ 100 but π^{2} ≈ 10  
is similar to^{[9]}

△ABC ~ △DEF means triangle ABC is similar to (has the same shape) triangle DEF.  
is asymptotically equivalent to

f ~ g means .  x ~ x+1  
are in the same equivalence class
everywhere

a ~ b means (and equivalently ).  1 ~ 5 mod 4
 

is defined as;
is equal by definition to everywhere

In definitions, the symbol "=" is preferred over "≡" or ":=". (see § Writing style in mathematics) x := y, y =: x or x ≡ y means x is defined to be another name for y, under certain assumptions taken in context. 
 
≅

\cong 
is congruent to

△ABC ≅ △DEF means triangle ABC is congruent to (has the same measurements as) triangle DEF.  
is isomorphic to

G ≅ H means that group G is isomorphic (structurally identical) to group H. (≈ can also be used for isomorphic, as described above.) 
V ≅ C_{2} × C_{2}  
\equiv 
... is congruent to ... modulo ...

a ≡ b (mod n) means a − b is divisible by n  5 ≡ 2 (mod 3)  
is identically equivalent to

for two functions f, g, means for all x.^{[10]}  
⇔
↔ 
\Leftrightarrow \iff \leftrightarrow 
if and only if;
iff 
A ⇔ B means A is true if B is true and A is false if B is false.  x + 5 = y + 2 ⇔ x + 3 = y 
:=
=: 
is defined to be
everywhere

A := b means A is defined to have the value b.  Let a := 3, then... f(x) := x + 3 
Symbol in HTML 
Symbol in TeX 
Name  Explanation  Examples 

Read as  
Category  
is less than,
is greater than 
means x is less than y. means x is greater than y. 
 
is a proper subgroup of

means H is a proper subgroup of G.   
\ll \gg 
significant (strict) inequality
is much less than,
is much greater than 
x ≪ y means x is much less than y. x ≫ y means x is much greater than y. 
0.003 ≪ 1000000  
asymptotic comparison
is of smaller order than,
is of greater order than 
f ≪ g means the growth of f is asymptotically bounded by g. (This is I. M. Vinogradov's notation. Another notation is the Big O notation, which looks like f = O(g).) 
x ≪ e^{x}  
absolute continuity
is absolutely continuous with respect to

means that is absolutely continuous with respect to , i.e., whenever , we have .  If is the counting measure on and is the Lebesgue measure, then .  
\le \ge 
is less than or equal to,
is greater than or equal to 
x ≤ y means x is less than or equal to y. x ≥ y means x is greater than or equal to y. (The forms <= and >= are generally used in programming languages, where ease of typing and use of ASCII text is preferred.) (≦ and ≧ are also used by some writers to mean the same thing as ≤ and ≥, but this usage seems to be less common.) 
3 ≤ 4 and 5 ≤ 5 5 ≥ 4 and 5 ≥ 5  
is a subgroup of

H ≤ G means H is a subgroup of G.  Z ≤ Z A_{3} ≤ S_{3}  
is reducible to

A ≤ B means the problem A can be reduced to the problem B. Subscripts can be added to the ≤ to indicate what kind of reduction.  If
then  
≦
≧ 
\leqq \geqq 
... is less than ... is greater than ...

10a ≡ 5 (mod 5) for 1 ≦ a ≦ 10  
... is less than or equal... is greater than or equal...

x ≦ y means that each component of vector x is less than or equal to each corresponding component of vector y. x ≧ y means that each component of vector x is greater than or equal to each corresponding component of vector y. It is important to note that x ≦ y remains true if every element is equal. However, if the operator is changed, x ≤ y is true if and only if x ≠ y is also true. 

≺
≻ 
\prec \succ 
is Karp reducible to;
is polynomialtime manyone reducible to 
L_{1} ≺ L_{2} means that the problem L_{1} is Karp reducible to L_{2}.^{[11]}  If L_{1} ≺ L_{2} and L_{2} ∈ P, then L_{1} ∈ P. 
is nondominated by

P ≺ Q means that the element P is nondominated by element Q.^{[12]}  If P_{1} ≺ Q_{2} then  
◅
▻ ◅ ▻ 
\triangleleft \triangleright 
is a normal subgroup of

N ◅ G means that N is a normal subgroup of group G.  Z(G) ◅ G 
is an ideal of

I ◅ R means that I is an ideal of ring R.  (2) ◅ Z  
the antijoin of

R ▻ S means the antijoin of the relations R and S, the tuples in R for which there is not a tuple in S that is equal on their common attribute names.  
⇒
→ ⊃ 
\Rightarrow \rightarrow \supset 
implies;
if ... then 
A ⇒ B means if A is true then B is also true; if A is false then nothing is said about B. (→ may mean the same as ⇒, or it may have the meaning for functions given below.) (⊃ may mean the same as ⇒,^{[13]} or it may have the meaning for superset given below.) 
x = 6 ⇒ x^{2} − 5 = 36 − 5 = 31 is true, but x^{2} − 5 = 36 −5 = 31 ⇒ x = 6 is in general false (since x could be −6). 
⊆
⊂ 
\subseteq \subset 
is a subset of

(subset) A ⊆ B means every element of A is also an element of B.^{[14]} (proper subset) A ⊂ B means A ⊆ B but A ≠ B. (Some writers use the symbol ⊂ as if it were the same as ⊆.) 
(A ∩ B) ⊆ A ℕ ⊂ ℚ ℚ ⊂ ℝ 
⊇
⊃ 
\supseteq \supset 
is a superset of

A ⊇ B means every element of B is also an element of A. A ⊃ B means A ⊇ B but A ≠ B. (Some writers use the symbol ⊃ as if it were the same as ⊇.) 
(A ∪ B) ⊇ B ℝ ⊃ ℚ 
\Subset 
is compactly contained in

A ⋐ B means the closure of A is a compact subset of B.  
\to 
function arrow
from ... to

f: X → Y means the function f maps the set X into the set Y.  Let f: ℤ → ℕ ∪ {0} be defined by f(x) := x^{2}.  
↦

\mapsto 
function arrow
maps to

f: a ↦ b means the function f maps the element a to the element b.  Let f: x ↦ x + 1 (the successor function). 
←

\leftarrow 
.. if ..

a ← b means that for the propositions a and b, if b implies a, then a is the converse implication of b.a to the element b. This reads as "a if b", or "not b without a". It is not to be confused with the assignment operator in computer science.  
<:
<· 
is a subtype of

T_{1} <: T_{2} means that T_{1} is a subtype of T_{2}.  If S <: T and T <: U then S <: U (transitivity).  
is covered by

x <• y means that x is covered by y.  {1, 8} <• {1, 3, 8} among the subsets of {1, 2, ..., 10} ordered by containment.  
⊧

\vDash 
entails

A ⊧ B means the sentence A entails the sentence B, that is in every model in which A is true, B is also true.  A ⊧ A ∨ ¬A 
⊢

\vdash 
infers;
is derived from 
x ⊢ y means y is derivable from x.  A → B ⊢ ¬B → ¬A 
is a partition of

p ⊢ n means that p is a partition of n.  (4,3,1,1) ⊢ 9,  
⟨

\langle 
the bra ...;
the dual of ... 
⟨φ means the dual of the vector φ⟩, a linear functional which maps a ket ψ⟩ onto the inner product ⟨φψ⟩.  
⟩

\rangle 
the ket ...;
the vector ... 
φ⟩ means the vector with label φ, which is in a Hilbert space.  A qubit's state can be represented as α0⟩+ β1⟩, where α and β are complex numbers s.t. α^{2} + β^{2} = 1. 
Symbol in HTML 
Symbol in TeX 
Name  Explanation  Examples 

Read as  
Category  
{\ \choose\ } 
n choose k

means (in the case of n = positive integer) the number of combinations of k elements drawn from a set of n elements. (This may also be written as C(n, k), C(n; k), _{n}C_{k}, ^{n}C_{k}, or .) 
 
\left(\!\!{\ \choose\ }\!\!\right) 
u multichoose k



\left\{ \begin{array}{lr} \ldots \\ \ldots \end{array}\right. 
is defined as ... if ..., or as ... if ...;
match ... with everywhere

means the function f(x) is defined as a if the condition p(x) holds, or as b if the condition q(x) holds. (The body of a piecewisedefined function can have any finite number (not only just two) expressioncondition pairs.) This symbol is also used in type theory for pattern matching the constructor of the value of an algebraic type. For example does pattern matching on the function's arguments and means that g(x) is defined as a, and g(y) is defined as b. (A pattern matching can have any finite number (not only just two) patternexpression pairs.) 

...

 \ldots  \!\, 
absolute value;
modulus absolute value of; modulus of

x means the distance along the real line (or across the complex plane) between x and zero.  3 = 3 –5 = 5 = 5  i  = 1  3 + 4i  = 5 
Euclidean norm or Euclidean length or magnitude
Euclidean norm of

x means the (Euclidean) length of vector x.  For x = (3,−4)  
determinant of

A means the determinant of the matrix A  
cardinality of;
size of; order of 
X means the cardinality of the set X. (# may be used instead as described below.) 
{3, 5, 7, 9} = 4.  
‖...‖

\ \ldots \ \!\, 
norm of;
length of 
‖ x ‖ means the norm of the element x of a normed vector space.^{[15]}  ‖ x + y ‖ ≤ ‖ x ‖ + ‖ y ‖ 
nearest integer to

‖x‖ means the nearest integer to x. (This may also be written [x], ⌊x⌉, nint(x) or Round(x).) 
‖1‖ = 1, ‖1.6‖ = 2, ‖−2.4‖ = −2, ‖3.49‖ = 3  
{\{\ ,\!\ \}} \!\, 
set brackets
the set of ...

{a,b,c} means the set consisting of a, b, and c.^{[16]}  ℕ = { 1, 2, 3, ... }  
{ : }
{  } { ; } 
\{\ :\ \} \!\, \{\ \ \} \!\, \{\ ;\ \} \!\, 
the set of ... such that

{x : P(x)} means the set of all x for which P(x) is true.^{[16]} {x  P(x)} is the same as {x : P(x)}.  {n ∈ ℕ : n^{2} < 20} = { 1, 2, 3, 4 } 
⌊...⌋

\lfloor \ldots \rfloor \!\, 
floor;
greatest integer; entier 
⌊x⌋ means the floor of x, i.e. the largest integer less than or equal to x. (This may also be written [x], floor(x) or int(x).) 
⌊4⌋ = 4, ⌊2.1⌋ = 2, ⌊2.9⌋ = 2, ⌊−2.6⌋ = −3 
⌈...⌉

\lceil \ldots \rceil \!\, 
ceiling

⌈x⌉ means the ceiling of x, i.e. the smallest integer greater than or equal to x. (This may also be written ceil(x) or ceiling(x).) 
⌈4⌉ = 4, ⌈2.1⌉ = 3, ⌈2.9⌉ = 3, ⌈−2.6⌉ = −2 
⌊...⌉

\lfloor \ldots \rceil \!\, 
nearest integer to

⌊x⌉ means the nearest integer to x. (This may also be written [x], x, nint(x) or Round(x).) 
⌊2⌉ = 2, ⌊2.6⌉ = 3, ⌊−3.4⌉ = −3, ⌊4.49⌉ = 4 
[ : ]

[\ :\ ] \!\, 
the degree of

[K : F] means the degree of the extension K : F.  [ℚ(√2) : ℚ] = 2 [ℂ : ℝ] = 2 [ℝ : ℚ] = ∞ 
[\ ] \!\, [\ ,\ ] \!\, 
the equivalence class of

[a] means the equivalence class of a, i.e. {x : x ~ a}, where ~ is an equivalence relation. [a]_{R} means the same, but with R as the equivalence relation. 
Let a ~ b be true iff a ≡ b (mod 5).
Then [2] = {..., −8, −3, 2, 7, ...}.  
floor;
greatest integer; entier 
[x] means the floor of x, i.e. the largest integer less than or equal to x. (This may also be written ⌊x⌋, floor(x) or int(x). Not to be confused with the nearest integer function, as described below.) 
[3] = 3, [3.5] = 3, [3.99] = 3, [−3.7] = −4  
nearest integer to

[x] means the nearest integer to x. (This may also be written ⌊x⌉, x, nint(x) or Round(x). Not to be confused with the floor function, as described above.) 
[2] = 2, [2.6] = 3, [−3.4] = −3, [4.49] = 4  
1 if true, 0 otherwise

[S] maps a true statement S to 1 and a false statement S to 0.  [0=5]=0, [7>0]=1, [2 ∈ {2,3,4}]=1, [5 ∈ {2,3,4}]=0  
image of ... under ...
everywhere

f[X] means { f(x) : x ∈ X }, the image of the function f under the set X ⊆ dom(f). (This may also be written as f(X) if there is no risk of confusing the image of f under X with the function application f of X. Another notation is Im f, the image of f under its domain.) 

closed interval

.  0 and 1/2 are in the interval [0,1].  
the commutator of

[g, h] = g^{−1}h^{−1}gh (or ghg^{−1}h^{−1}), if g, h ∈ G (a group). [a, b] = ab − ba, if a, b ∈ R (a ring or commutative algebra). 
x^{y} = x[x, y] (group theory). [AB, C] = A[B, C] + [A, C]B (ring theory).  
the triple scalar product of

[a, b, c] = a × b · c, the scalar product of a × b with c.  [a, b, c] = [b, c, a] = [c, a, b].  
(\ ) \!\, (\ ,\ ) \!\, 
function application
of

f(x) means the value of the function f at the element x.  If f(x) := x^{2} − 5, then f(6) = 6^{2} − 5 = 36 − 5=31.  
image of ... under ...
everywhere

f(X) means { f(x) : x ∈ X }, the image of the function f under the set X ⊆ dom(f). (This may also be written as f[X] if there is a risk of confusing the image of f under X with the function application f of X. Another notation is Im f, the image of f under its domain.) 

precedence grouping
parentheses
everywhere

Perform the operations inside the parentheses first.  (8/4)/2 = 2/2 = 1, but 8/(4/2) = 8/2 = 4.  
everywhere

An ordered list (or sequence, or horizontal vector, or row vector) of values.
(Note that the notation (a,b) is ambiguous: it could be an ordered pair or an open interval. Set theorists and computer scientists often use angle brackets ⟨ ⟩ instead of parentheses.) 
(a, b) is an ordered pair (or 2tuple).
(a, b, c) is an ordered triple (or 3tuple). ( ) is the empty tuple (or 0tuple).  
highest common factor;
greatest common divisor; hcf; gcd number theory

(a, b) means the highest common factor of a and b. (This may also be written hcf(a, b) or gcd(a, b).) 
(3, 7) = 1 (they are coprime); (15, 25) = 5.  
( , )
] , [ 
(\ ,\ ) \!\,(\ ,\ ) \!\, ]\ ,\ [ \!\,] 
open interval

.
(Note that the notation (a,b) is ambiguous: it could be an ordered pair or an open interval. The notation ]a,b[ can be used instead.) 
4 is not in the interval (4, 18).
(0, +∞) equals the set of positive real numbers. 
( , ]
] , ] 
(\ ,\ ] \!\, \ ,\ ] \!\,] 
halfopen interval;
leftopen interval 
.  (−1, 7] and (−∞, −1] 
[ , )
[ , [ 
[\ ,\ ) \!\, [\ ,\ [ \!\, 
halfopen interval;
rightopen interval 
.  [4, 18) and [1, +∞) 
⟨⟩
⟨,⟩ 
\langle\ \rangle \!\, \langle\ ,\ \rangle \!\, 
inner product of

⟨u,v⟩ means the inner product of u and v, where u and v are members of an inner product space. Note that the notation ⟨u, v⟩ may be ambiguous: it could mean the inner product or the linear span. There are many variants of the notation, such as ⟨u  v⟩ and (u  v), which are described below. For spatial vectors, the dot product notation, x · y is common. For matrices, the colon notation A : B may be used. As ⟨ and ⟩ can be hard to type, the more "keyboard friendly" forms < and > are sometimes seen. These are avoided in mathematical texts. 
The standard inner product between two vectors x = (2, 3) and y = (−1, 5) is: ⟨x, y⟩ = 2 × −1 + 3 × 5 = 13 
average
average of

let S be a subset of N for example, represents the average of all the elements in S.  for a time series :g(t) (t = 1, 2,...)
we can define the structure functions S_{q}():  
the expectation value of

For a single discrete variable of a function , the expectation value of is defined as , and for a single continuous variable the expectation value of is defined as ; where is the PDF of the variable .^{[17]}  
(linear) span of;
linear hull of 
⟨S⟩ means the span of S ⊆ V. That is, it is the intersection of all subspaces of V which contain S. ⟨u_{1}, u_{2}, ...⟩ is shorthand for ⟨{u_{1}, u_{2}, ...}⟩.

.  
subgroup generated by a set
the subgroup generated by

means the smallest subgroup of G (where S ⊆ G, a group) containing every element of S. is shorthand for . 
In S_{3}, and .  
tuple; ntuple;
ordered pair/triple/etc; row vector; sequence everywhere

An ordered list (or sequence, or horizontal vector, or row vector) of values.
(The notation (a,b) is often used as well.) 
is an ordered pair (or 2tuple).
is an ordered triple (or 3tuple). is the empty tuple (or 0tuple).  
⟨⟩
() 
\langle\ \ \rangle \!\, (\ \ ) \!\, 
inner product of

⟨u  v⟩ means the inner product of u and v, where u and v are members of an inner product space.^{[18]} (u  v) means the same. Another variant of the notation is ⟨u, v⟩ which is described above. For spatial vectors, the dot product notation, x · y is common. For matrices, the colon notation A : B may be used. As ⟨ and ⟩ can be hard to type, the more "keyboard friendly" forms < and > are sometimes seen. These are avoided in mathematical texts. 
Symbol in HTML 
Symbol in TeX 
Name  Explanation  Examples 

Read as  
Category  
\ast or * 
convolution;
convolved with 
f∗g means the convolution of f and g. (Different than f*g, which means the product of g with the complex conjugate of f, as described below.) (Can also be written in text as f ∗ g.) 
.  
Hodge star;
Hodge dual 
∗v means the Hodge dual of a vector v. If v is a kvector within an ndimensional oriented quadratic space, then ∗v is an (n−k)vector.  If are the standard basis vectors of ,  
^\ast or ^* 
conjugate

z* means the complex conjugate of z. ( can also be used for the conjugate of z, as described below.) 
.  
the group of units of

R^{∗} consists of the set of units of the ring R, along with the operation of multiplication. This may also be written R^{×} as described above, or U(R). 

the (set of) hyperreals

^{∗}R means the set of hyperreal numbers. Other sets can be used in place of R.  ^{∗}N is the hypernatural numbers.  
Kleene star

Corresponds to the usage of * in regular expressions. If ∑ is a set of strings, then ∑* is the set of all strings that can be created by concatenating members of ∑. The same string can be used multiple times, and the empty string is also a member of ∑*.  If ∑ = ('a', 'b', 'c') then ∑* includes '', 'a', 'ab', 'aba', 'abac', etc. The full set cannot be enumerated here since it is countably infinite, but each individual string must have finite length.  
\propto \!\, 
is proportional to;
varies as everywhere

y ∝ x means that y = kx for some constant k.  if y = 2x, then y ∝ x.  
Karp reduction^{[19]}
is Karp reducible to;
is polynomialtime manyone reducible to 
A ∝ B means the problem A can be polynomially reduced to the problem B.  If L_{1} ∝ L_{2} and L_{2} ∈ P, then L_{1} ∈ P.  
∖

\setminus 
minus;
without; throw out; not 
A ∖ B means the set that contains all those elements of A that are not in B.^{[14]} (− can also be used for settheoretic complement as described above.) 
{1,2,3,4} ∖ {3,4,5,6} = {1,2} 
given

P(AB) means the probability of the event A occurring given that B occurs.  if X is a uniformly random day of the year P(X is 25  X is in May) = 1/31  
restriction of ... to ...;
restricted to 
f_{A} means the function f is restricted to the set A, that is, it is the function with domain A ∩ dom(f) that agrees with f.  The function f : R → R defined by f(x) = x^{2} is not injective, but f_{R+} is injective.  
such that
such that;
so that everywhere

 means "such that", see ":" (described below).  S = {(x,y)  0 < y < f(x)} The set of (x,y) such that y is greater than 0 and less than f(x).  
∣
∤ 
\mid \nmid 
divides

a ∣ b means a divides b. a ∤ b means a does not divide b. (The symbol ∣ can be difficult to type, and its negation is rare, so a regular but slightly shorter vertical bar  character is often used instead.) 
Since 15 = 3 × 5, it is true that 3 ∣ 15 and 5 ∣ 15. 
∣∣

\mid\mid 
exact divisibility
exactly divides

p^{a} ∣∣ n means p^{a} exactly divides n (i.e. p^{a} divides n but p^{a+1} does not).  2^{3} ∣∣ 360. 
∥
∦ ⋕ 
\ Requires the viewer to support Unicode: \unicode{x2225}, \unicode{x2226}, and \unicode{x22D5}. \mathrel{\rlap{\,\parallel}} requires \setmathfont{MathJax}.^{[20]} 
is parallel to

x ∥ y means x is parallel to y. x ∦ y means x is not parallel to y. x ⋕ y means x is equal and parallel to y. (The symbol ∥ can be difficult to type, and its negation is rare, so two regular but slightly longer vertical bar  characters are often used instead.) 
If l ∥ m and m ⊥ n then l ⊥ n. 
is incomparable to

x ∥ y means x is incomparable to y.  {1,2} ∥ {2,3} under set containment.  
\sharp 
cardinality of;
size of; order of 
#X means the cardinality of the set X. (... may be used instead as described above.) 
#{4, 6, 8} = 3  
connected sum of;
knot sum of; knot composition of 
A#B is the connected sum of the manifolds A and B. If A and B are knots, then this denotes the knot sum, which has a slightly stronger condition.  A#S^{m} is homeomorphic to A, for any manifold A, and the sphere S^{m}.  
primorial

n# is product of all prime numbers less than or equal to n.  12# = 2 × 3 × 5 × 7 × 11 = 2310  
such that
such that;
so that everywhere

: means "such that", and is used in proofs and the setbuilder notation (described below).  ∃ n ∈ ℕ: n is even.  
extends;
over 
K : F means the field K extends the field F. This may also be written as K ≥ F. 
ℝ : ℚ  
inner product of matrices
inner product of

A : B means the Frobenius inner product of the matrices A and B. The general inner product is denoted by ⟨u, v⟩, ⟨u  v⟩ or (u  v), as described below. For spatial vectors, the dot product notation, x·y is common. See also bra–ket notation. 

index of subgroup

The index of a subgroup H in a group G is the "relative size" of H in G: equivalently, the number of "copies" (cosets) of H that fill up G  
divided by
over everywhere

A : B means the division of A with B (dividing A by B)  10 : 2 = 5  
⋮

\vdots \!\, 
vertical ellipsis
everywhere

Denotes that certain constants and terms are missing out (e.g. for clarity) and that only the important terms are being listed.  
≀

\wr \!\, 
wreath product of ... by ...

A ≀ H means the wreath product of the group A by the group H. This may also be written A_{ wr }H. 
is isomorphic to the automorphism group of the complete bipartite graph on (n,n) vertices. 
↯
⨳ ⇒⇐ 
\blitza \lightning: requires \usepackage{stmaryrd}.^{[21]} \smashtimes requires \usepackage{unicodemath} and \setmathfont{XITS Math} or another Open Type Math Font.^{[22]} ^{[2]} ^{[2]} \textreferencemark^{[2]} 
contradiction; this contradicts that
everywhere

Denotes that contradictory statements have been inferred. For clarity, the exact point of contradiction can be appended.  x + 4 = x − 3 ※ Statement: Every finite, nonempty, ordered set has a largest element. Otherwise, let's assume that is a finite, nonempty, ordered set with no largest element. Then, for some , there exists an with , but then there's also an with , and so on. Thus, are distinct elements in . ↯ is finite. 
⊕
⊻ 
\oplus \!\, \veebar \!\, 
xor

The statement A ⊕ B is true when either A or B, but not both, are true. A ⊻ B means the same.  (¬A) ⊕ A is always true, A ⊕ A is always false. 
direct sum of

The direct sum is a special way of combining several objects into one general object. (The bun symbol ⊕, or the coproduct symbol ∐, is used; ⊻ is only for logic.) 
Most commonly, for vector spaces U, V, and W, the following consequence is used: U = V ⊕ W ⇔ (U = V + W) ∧ (V ∩ W = {0})  
{~\wedge\!\!\!\!\!\!\!\!\;\bigcirc~} 
Kulkarni–Nomizu product

Derived from the tensor product of two symmetric type (0,2) tensors; it has the algebraic symmetries of the Riemann tensor. has components .  
□

\Box \!\ 
D'Alembertian;
wave operator nonEuclidean Laplacian

It is the generalisation of the Laplace operator in the sense that it is the differential operator which is invariant under the isometry group of the underlying space and it reduces to the Laplace operator if restricted to time independent functions. 
Includes upsidedown letters.
Also called diacritics.
Symbol in HTML 
Symbol in TeX 
Name  Explanation  Examples 

Read as  
Category  
\bar{a} 
overbar;
... bar 
(often read as "x bar") is the mean (average value of ).  .  
finite sequence, tuple

means the finite sequence/tuple .  .  
algebraic closure of

is the algebraic closure of the field F.  The field of algebraic numbers is sometimes denoted as because it is the algebraic closure of the rational numbers .  
conjugate

means the complex conjugate of z. (z^{∗} can also be used for the conjugate of z, as described above.) 
.  
(topological) closure of

is the topological closure of the set S. This may also be denoted as cl(S) or Cl(S). 
In the space of the real numbers, (the rational numbers are dense in the real numbers).  
\overset{\rightharpoonup}{a} 
harpoon


â

\hat a 
hat

(pronounced "a hat") is the normalized version of vector , having length 1.  
estimator for

is the estimator or the estimate for the parameter .  The estimator produces a sample estimate for the mean .  
' 
... prime;
derivative of 
f ′(x) means the derivative of the function f at the point x, i.e., the slope of the tangent to f at x. (The singlequote character ' is sometimes used instead, especially in ASCII text.) 
If f(x) := x^{2}, then f ′(x) = 2x.  
\dot{\,} 
... dot;
time derivative of 
means the derivative of x with respect to time. That is .  If x(t) := t^{2}, then . 
Symbol in HTML 
Symbol in TeX 
Name  Explanation  Examples 

Read as  
Category
 
\forall 
for all;
for any; for each; for every 
∀ x, P(x) means P(x) is true for all x.  ∀ n ∈ ℕ, n^{2} ≥ n.  