Roman letters used in mathematics

Monday 24 December 2012



Many Roman letters, both capital and small, are used in mathematics, science and engineering to denote by convention specific or abstracted constants, variables of a certain type, units, multipliers, physical entities. Certain letters, when combined with special formatting, take on special meaning.

Below is an alphabetical list of the letters of the alphabet with some of their uses. The field in which the convention applies is mathematics unless otherwise noted.

Aa

  • A represents:
    • the first corner of a triangle
    • the digit "10" in hexadecimal and other positional numeral systems with a radix of 11 or greater
    • the unit ampere for electrical current
    • area
  • represents the algebraic numbers or affine space in Algebraic Geometry
  • a represents:
    • the first side of a triangle (opposite corner A)
    • the acceleration in mechanics equations
    • the x-intercept of a line
    • the unit are for area (100 m²)
    • the unit prefix atto (10−18)
    • the first term in a sequence or series (eg. Sn = n(a+l)/2)
Bb

  • B represents:
    • the digit "11" in hexadecimal and other positional numeral systems with a radix of 12 or greater
    • the second corner of a triangle
    • a ball (also denoted by or )
    • a basis of a vector space or of a filter (both also denoted by )
  • B with various subscripts represents several variations of Brun's constant and Betti numbers
  • b represents:
    • the second side of a triangle (opposite corner B)
    • the y-intercept of a line
    • (usually with an index, sometimes with an arrow over it) a basis vector

 Cc

  • C represents:
    • the third corner of a triangle
    • the digit "12" in hexadecimal and other positional numeral systems with a radix of 13 or greater
    • the unit coulomb of electrical charge
  • C with indices denotes the number of combinations, a binomial coefficient
  • represents the set of complex numbers
  • A vertically elongated C with an integer subscript n sometimes denotes the n-th coefficient of a formal power series.
  • c represents:
    • the third side of a triangle (opposite corner C)
    • the unit prefix centi (10−2)
  • c represents:
  • Small bold C denotes the cardinality of the set of real numbers (the "continuum"), or,
equivalently, of the power set of natural numbers

 Dd

  • D represents the digit "13" in hexadecimal and other positional numeral systems with a radix of 14 or greater
  • d represents
    • the differential operator
    • the unit day of time (86 400 s)
    • the difference in an arithmetic sequence (eg. Sn = n(2a+(n-1)d)/2)

 Ee

  • E represents:
    • the digit "14" in hexadecimal and other positional numeral systems with a radix of 15 or greater
    • an exponent in decimal numbers 1.2E3 is 1.2×10³ or 1200
    • the set of edges in a graph or matroid
    • the unit prefix exa (1018)
    • Energy in physics
  • e represents:
    • Euler's number, a transcendental number equal to 2.71828182845… which is used as the base for natural logarithms
    • a vector of unit length, especially in the direction of one of the coordinates axes
    • the elementary charge in physics

Ff


 Gg


 Hh


Ii

  • I represents:
    • the closed unit interval, which contains all real numbers from 0 to 1, inclusive
    • the identity matrix
  • i represents:
    • the imaginary unit, a complex number that is the square root of −1
    • a subscript to denote the ith term (that is, a general term or index) in a sequence or list
    • the index to the elements of a vector, written as a subscript after the vector name
    • the index to the rows of a matrix, written as the first subscript after the matrix name
    • an index of summation using the sigma notation
Jj
  • J represents the unit joule of energy
  • j represents:

 Kk


 Ll

  • L represents:
    • the unit litre of volume
    • the space of all integrable real (or complex) functions
    • the space of linear maps, as in L(E,F) or L(E) = End(E)
    • the Likelihood function
  • l represents:
    • the length of a side of a rectangle or a rectangular prism (eg. V = lwh; A = lw)
    • the last term of a sequence or series (eg. Sn = n(a+l)/2)
  • (or sometimes just L) represents the Lagrangian

 Mm

  • M represents:
  • m represents:
    • the number of rows in a matrix
    • the slope in a linear regression or in any line
    • the mass in mechanics equations
    • the unit metre of length
    • the unit prefix milli (10−3)

Nn

  • N represents
  • NA represents the Avogadro constant which is the number of entities in one mole (used mainly in the counting of molecules and atoms)
  • represents the natural numbers
  • n represents
    • the number of columns in a matrix
    • the "number of" in algebraic equations.
    • the unit prefix nano (10−9)
    • the nth term of a sequence or series (eg. tn = a+(n-1)d)

 Oo

  • O represents the order of asymptotic behavior of a function; see Big O notation
  • O represents — the origin of the coordinate system in Cartesian coordinates

 Pp


 Qq


 Rr

  • R represents:
  • represents the set of real numbers and various algebraic structures built upon the set of real numbers, such as
  • r represents:
    • the radius of a circle or sphere
    • the ratio of a geometric series (eg. arn-1)

 Ss

  • S represents
  • s represents:
    • an arclength
    • the distance traveled in mechanics equations
    • the unit second of time
  • represents a system's action in physics

Tt

  • T represents:
  • t represents:
    • time in graphs, functions or equations
    • a term in a sequence or series (eg. tn = tn-1+5)

 Uu


 Vv

  • V represents:
    • volume
    • the unit volt of voltage
    • the set of vertices in a graph
  • v represents the velocity in mechanics equations

 Ww

  • W represents the unit watt of power

 Xx


Yy

  • Y represents:
    • the unit prefix yotta (1024)
  • y represents:
    • the unit prefix yocto (10−24)
  • y represents:
    • a second unknown variable
    • the coordinate on the second or vertical axis (backward axis in three dimensions) in a linear coordinate system, or in the viewport of a graph or window in computer graphics

 Zz

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Logic symbols



In logic, a set of symbols is commonly used to express logical representation. As logicians are familiar with these symbols, they are not explained each time they are used. So, for students of logic, the following table lists many common symbols together with their name, pronunciation and related field of mathematics. Additionally, the third column contains an informal definition, and the fourth column gives a short example.

Be aware that, outside of logic, different symbols have the same meaning, and the same symbol has, depending on the context, different meanings.

 Basic logic symbols

Symbol
Name
Explanation
Examples
Unicode
Value
HTML
Entity
LaTeX
symbol
Should be read as
Category




AB 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 ⇒ (the symbol may also indicate the domain and codomain of a function; see table of mathematical symbols).

⊃ may mean the same as ⇒ (the symbol may also mean superset).
x = 2  ⇒  x2 = 4 is true, but x2 = 4   ⇒  x = 2 is in general false (since x could be −2).
8658

8594

8835
⇒
→
⊃
\Rightarrow
\rightarrow
\supset
implies; if .. then




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
8660

8801

8596
⇔
≡
↔
\Leftrightarrow
\equiv
\leftrightarrow
if and only if; iff
¬

˜
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.
¬(¬A) ⇔ A
x ≠ y  ⇔  ¬(x =  y)
172

732
¬
˜
~
\lnot
\tilde{}
not


&
The statement AB is true if A and B are both true; else it is false.
n < 4  ∧  n >2  ⇔  n = 3 when n is a natural number.
8743

38
&and;
&
\land
\&[1]
and
The statement AB is true if A or B (or both) are true; if both are false, the statement is false.
n ≥ 4  ∨  n ≤ 2  ⇔ n ≠ 3 when n is a natural number.
8744
&or;
\lor
or



The statement AB is true when either A or B, but not both, are true. A B means the same.
A) ⊕ A is always true, AA is always false.
8853

8891
&oplus;
\oplus
xor



T

1
logical truth
The statement is unconditionally true.
A is always true.
8868
T
\top
top



F

0
logical falsity
The statement ⊥ is unconditionally false.
⊥ ⇒ A is always true.
8869
&perp;
F
\bot
bottom
∀ x: P(x) means P(x) is true for all x.
∀ n ∈ N: n2 ≥ n.
8704
&forall;
\forall
for all; for any; for each
∃ x: P(x) means there is at least one x such that P(x) is true.
∃ n ∈ N: n is even.
8707
&exist;
\exists
there exists
∃!
∃! x: P(x) means there is exactly one x such that P(x) is true.
∃! n ∈ N: n + 5 = 2n.
8707 33
&exist; !
\exists !
there exists exactly one
:=



:⇔
x := y or x ≡ y means x is defined to be another name for y (but note that ≡ can also mean other things, such as congruence).

P :⇔ Q means P is defined to be logically equivalent to Q.
cosh x := (1/2)(exp x + exp (−x))

A XOR B :⇔ (A ∨ B) ∧ ¬(A ∧ B)
58 61

8801

58 8660
 :=
: &equiv;
&hArr;
: = :=
\equiv
\Leftrightarrow
is defined as
everywhere
( )
precedence grouping
Perform the operations inside the parentheses first.
(8/4)/2 = 2/2 = 1, but 8/(4/2) = 8/2 = 4.
40 41
( )
( )

everywhere
x y means y is derived from x.
AB ¬B → ¬A
8866

\vdash
infers or is derived from

 See also

·      Polish notation

 Special characters

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