Polynomials (many terms) are algebraic expressions formed by adding or subtracting monomials (single terms with positive exponents or constants). A Binomial is a polynomial containing two terms, bi meaning two.
In terms of nomenclature, 'bi' means 2 hence binomial means two terms. So in general, a binomial is a polynomial containing two terms. The general form can be written as axn ± bym
A different and simpler way of defining a binomial is that it is an algebraic expression containing two terms connected by a sum of a difference sign. Example: 3x+5y,a+3x, x2-3x…etc.