This document defines key terms in algebra, including algebraic expressions, equations, monomials, binomials, trinomials, variables, constants, coefficients, and operators. It provides examples of each term and notes that monomials have one term, binomials have two terms, and trinomials have three terms. Variables represent unknown quantities, coefficients are numbers that multiply variables, and constants are numbers that remain unchanged. Operators indicate mathematical functions like addition and multiplication. Definitions are drawn from online math references and dictionaries.