In mathematics, a coefficient is a number or symbol that is multiplied by a variable in a single term or the terms of a polynomial, a series, or any expression. It can be a numerical factor or a constant with units of measurement. The coefficient attached to the highest degree of the variable in a polynomial is referred to as the leading coefficient. The constant coefficient, also known as the constant term, is the quantity not attached to variables in an expression. For example, in the expression 5x^2 + 2y - 7, the coefficient of x^2 is 5, the coefficient of y is 2, and the constant coefficient is -7. The variables that do not have a number with them are assumed to have 1 as their coefficient.