A simplified expression.
A polynomial is one possible answer.
It is in its simplified form.
An algebraic expression.
An algebraic expression need not be a difference of two terms.
It is called a "binomial."
they are called terms.
are the terms of the expression
An algebraic expression are terms that do not include an equality sign.
They may be algebraic terms.
An expression consists of algebraic terms and has no equality sign
An algebraic expression has 2 or more terms in it without an equality sign.