Mathematical expressions can be made up of variables, constants or a mix of both, but they must always represent values. The symbols in an expression are joined together by mathematical operations such as multiplication or division.

Although the term is associated strongly with algebra, children are taught mathematical expressions from the moment they are handed worksheets containing the simple expression "2 + 2."

Equations and inequalities are special mathematical statements that compare expressions. For example, while "2 + 2" is an expression, "2 + 2 = 4" is an equation.