ABSTRACT
In mathematics, a variable is an entity whose value or meaning can change, causing the evaluation of an expression to change. For instance, the venerated function for obtaining the instantaneous velocity of a falling body is
f(t) = gt,
where g = 9.8 m ⋅ s−2 and t = time in seconds. Both t and f(t) are variables. Any value greater than or equal to zero can be assigned to t, and f(t) will vary directly with t. In contrast, g is a constant with a single xed value.
