What is an expression that has only one term called?

An expression that consists of only one term is referred to as a monomial. Monomials are characterized by their simplicity, as they do not contain any addition or subtraction operations that would combine multiple terms. A monomial can be a single variable raised to a power, a constant, or the product of constants and variables.

Understanding monomials is foundational in algebra because they serve as the building blocks for more complex expressions. For instance, when creating polynomials, which can consist of one or more terms, monomials are often combined through addition to form these more complex expressions.

In contrast, a polynomial is defined as an expression that can have one or more monomial terms, whereas a binomial specifically contains two terms and a trinomial contains three. Since a monomial has only one term, this makes it distinctly different from the other types of expressions. This clarity in definition highlights why the term monomial is the accurate descriptor for an expression made up of a single term.