How can you tell if an expression is a monomial , binomial or trinomial?

Look at the Latin root. Mono means one, so is an example because it is only made up of one term. Bi means two, so +4 is an example because it was two terms. Tri means three, so there needs to be three terms for it to be a trinomial. -3x+5 is an example of a trinomial because it was three terms within the equation.

I hope this helps!