A polynomial is the sum of n monomials, for some whole number n . So monomials, binomials and trinomials are all special cases of polynomials.
A polynomial is an algebraic expression that has one, two or more terms.
A binomial is an algebraic expression that has two non-zero terms. Examples of a binomial expression:
a^2 + 2b is a binomial in two variables a and b.