binomial

A binomial is the sum of two monomial terms. It is a type of polynomial.

A binomial in a single indeterminate can be written in the form

a x^{m} + b x^{n}

where $a$ and $b$ are elements of a field called coefficients,
$m$ and $n$ are distinct non-negative integers,
and $x$ is an indeterminate.

The product of two linear binomials is a trinomial:

(a x + b y) (c x + d y) = a c x^{2} + (a d + b c) x y + b d y^{2}