Many letters of the Latin alphabet, 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, or 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 point of a triangle the digit "10" in hexadecimal and other positional numeral systems with a radix of 11 or greater the unit ampere for electric current in physics the area of a figure the mass number or nucleon number of an element in chemistry the Helmholtz free energy of a closed thermodynamic system of constant pressure and temperature a vector potential, in electromagnetics it can refer to the magnetic vector potential an Abelian group in abstract algebra the Glaisher–Kinkelin constant atomic weight, denoted by Ar work in classical mechanics the pre-exponential factor in the Arrhenius Equation electron affinity represents the algebraic numbers or affine space in algebraic geometry. A blood type A spectral type a represents: the first side of a triangle (opposite point A) the scale factor of the expanding universe in cosmology the acceleration in mechanics equations the first constant in a linear equation a constant in a polynomial the unit are for area (100 m2) the unit prefix atto (10−18) the first term in a sequence or series Reflectance
Bb
B represents: the digit "11" in hexadecimal and other positional numeral systems with a radix of 12 or greater the second point of a triangle a ball (also denoted by ℬ () or ) a basis of a vector space or of a filter (both also denoted by ℬ ()) in econometrics and time-series statistics it is often used for the backshift or lag operator, the formal parameter of the lag polynomial the magnetic field, denoted or B with various subscripts represents several variations of Brun's constant and Betti numbers; it can also be used to mean the Bernoulli numbers. B meson A blood type Boron Buoyancy Bulk modulus Luminance A spectral type b represents: the second side of a triangle (opposite point B) the impact parameter in nuclear scattering the second constant in a linear equation usually with an index, sometimes with an arrow over it, a basis vector a breadth the molality of a solution Bottom quark Barn ( cm)
Cc
C represents: the third point 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 capacitance in electrical theory with indices denoting the number of combinations, a binomial coefficient together with a degree symbol (°), the Celsius measurement of temperature = °C the circumference of a circle or other closed curve the complement of a set (lowercase c and the symbol ∁ are also used) an arbitrary category the number concentration* Carbon Heat capacity The C programming language Cunningham correction factor 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 unit prefix centi (10−2) the amount concentration in chemistry the speed of light in vacuum the third side of a triangle (opposite corner C) Lowercase Fraktur denotes the cardinality of the set of real numbers (the "continuum"), or, equivalently, of the power set of natural numbers. the third constant in a linear equation a constant in a polynomial Charm quark Speed of sound Specific heat capacity
Dd
D represents
the digit "13" in hexadecimal and other positional numeral systems with a radix of 14 or greater diffusion coefficient or diffusivity in dimensions of [distance2/time] the differential operator in Euler's calculus notation dissociation energy Dimension Deuterium Electric displacement D meson Density d represents the differential operator the unit day of time (86,400 s) the difference in an arithmetic sequence a metric operator/function the diameter of a circle the unit prefix deci (10−1) a thickness a distance Down quark Infinitesimal increment in calculus Density