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.
Mathematics is full of equations and expressions. A mathematical expression is a set of variables and constants that are connected together with the help of algebraic operations : such as - addition (+), subtraction (-), multiplication (x), division (/), exponentiation (^) etc. On the other hand, equation is defined as an expression with equal sign.