In Years 1 and 2 children will have worked mainly with halves, quarters and thirds. In Year 3 they will investigate other denominators. The term, ‘denominator’ will be introduced and that it shows how many equal parts the whole has been divided into. At first, this will be done with fractions known as ‘unit fractions’. These are fractions where the top number, or numerator is one. For example, one-fifth or one-ninth. Later ‘non-unit fractions are introduced: e.g. three-sevenths.

The terms numerator and denominator are tricky to understand, and it is more than likely that children will need to come across them many times before full understanding is achieved.