What does this expression represent 5-n

5 n = Algebraic expression 5 n is a Monomial, which is product of Constant Real number 5 and Variable n.

Also, you can say that this is Explicit formula for Arithmetic Sequence. That is general term or nth term = 5 n

For, n=1,2,3,4,5,. that is if n is any natural number,

5 n=5,10,15,20, 25,30,35,40, and so on

First term = 5

Common Difference = Second term - First term

10-5=5