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.
Now it is time to talk about equations. An expression is just a statement like. 2 x + 3. This expression might be equal to any number, depending on the choice of x. For example, if x = 3 then the value of this expression is 9. But if we are writing an equation, then we are making a statement about its value.