Collecting like terms means to simplify terms in expressions ... This means \(a \times a = a^2\) (read as 'a squared'). In \(a^2\), the 2 is known as the index number or power.

It may be possible to simplify an expression by collecting like terms together ... 4y\) and \(9y^2\) are not like terms but \(4y^2\) and \(9y^2\) are.