Algebraic expressions can be simplified by gathering like terms. Like terms are terms that feature the same variable, usually shown by a letter.

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**.