Definition of dray. : a vehicle used to haul goods; especially : a strong cart or wagon without sides.
Expressions versus Equations. A difference between expressions and equations is what each represents. An expression shows a math relationship. One key to an expression is that there is no solution. An expression does not have an answer. An expression, however, can be evaluated. To evaluate an expression, substitute values for the variables.
As stated above, the main difference between an equation and a function is that an equation usually has only one input that will give lead to the expressions being equal. Whereas, a function has various inputs, each of which will give a output.