If binary data can be thought of as two-valued variables, then nominal data can be expressed as n-valued variables.

Nominal data is discrete - a car is either a Porsche or it is not.

Certainly, eye color is a nominal variable, since it is multi-valued (blue, green, brown, grey, pink, black), and there is no clear scale on which to fit the different values.

Ordinal Data

Closely related to nominal data, ordinal data is multi-valued with an ordering relationship, where the actual distance between any two neighbor values is unknown.

Although this data may seem interval-based,
the ranges of each selection differ, and so it is not
necessarily the case that the interval (i,j) has the
same meaning across the entire
data set!

Nominal and Ordinal Data