# Algebraic terms and expressions

In algebra, letters are used to stand for values that can change (variables) or for values that aren’t known (unknowns), for example:

• $x$
• $a$
• $h$

A term is a number or letter on its own, or numbers and letters multiplied together, for example:

• $- 2$
• $3x$
• $y^2$

An expression is a set of terms combined using the operations $$+$$, $$-$$, $$\times$$ or $$\div$$, for example:

• $4x − 3$
• $5x + 2y$
• $a + 2b + c$

We can often simplify algebraic expressions so that they are shorter to read and write.

For example, the expression $$b + b + b + b$$ can be simplified to $$4b$$.

Simplifying an expression like this is called collecting like terms.