variable

In mathematics, a changing quantity (one that can take various values), as opposed to a constant. For example, in the algebraic expression y = 4x³ + 2, the variables are x and y, whereas 4 and 2 are constants.

A variable may be dependent or independent. Thus if y is a function of x, written y = f(x), such that y = 4x³ + 2, the domain of the function includes all values of the independent variable x while the range (or co-domain) of the function is defined by the values of the dependent variable y.