A nominal scale is a scale (of measurement) that uses labels to classify cases (measurements) into classes.

Some examples of variables that use nominal scales would be religious affiliation, sex, the city where you live, etc.

One example of a nominal scale could be "sex". For example, students in a class would fall into two possible classes, male or female.

A sample data set is given below left. Notice that it makes no difference if the order of categories is changed, as illustrated below right, since order is irrelevant with nominal data and nominal scales.