loose conventions of every letter of the alphabet when used in math, in my experience: a - variable, usually the first, or acceleration b - variable, usually the second, or a basis function c - constant, coefficient, or the speed of light, might be a third variable d - infinitesimal/derivative notation, but could also be distance or diameter. using this as a fourth variable after a, b, and c is illegal under international law e - euler's number, or a variable/constant if we're feeling extra brave f - function, probably g - probably also a function. or the scalar gravity constant h - a variable, usually height, but might be a function too i - the imaginary unit, if we're doing complex algebra/analysis, or a basis vector. could also be an integer j - quaternion basis or basis vector k - quaternion basis or basis vector l - mostly unused, bad glyph, nobody likes it, too similar to 1 and | and I. you may use it only if you write it very squiggly cursively or for lagrange polynomials m - a constant, or mass n - an integer, or a normal vector o - mostly unused? if I see this I'm probably reading my own notes p - a constant, usually an intermediate variable q - a quaternion, or an intermediate variable r - a radius, or a position vector s - displacement or arc length t - time or interpolation parameter, usually as an independent variable in a parametric equation, or a tangent vector u - a coordinate in 2D space, or the first parameter of a parametric function with more than one parameter, or a time/interpolation value v - a vector, might be a velocity vector specifically, or scalar speed, or a coordinate in 2D space, or the second parameter of a parametric function w - the real part of a quaternion, or a phase/angular velocity/frequency x - an independent variable or the first component of a coordinate/vector in 2D or 3D space y - a dependent variable or the second component of a coordinate/vector in 2D or 3D space z - a complex number, or the third component of a coordinate/vector in 3D space