Definition of dray. : a vehicle used to haul goods; especially : a strong cart or wagon without sides.
The main difference between an equation and a function is the fact that an equation usually deals with a single input, whereas, a function can have numerous inputs. In mathematics, an equation is used to denote the equality between two expressions.
An equation is a mathematical statement that two expressions are equal. In a simple numerical equation, expressions made of numbers and operations appear on each side of an equals sign. The equals sign means that the two expressions have the same value. For example, 3 + 9 = 12 is an equation.