Which scale is the simplest form of measurement?

The nominal scale is the simplest form of measurement, merely labelling categories.

The ordinal scale adds rank order but not equal intervals between values.

The interval scale has equal intervals yet no true zero point.

The ratio scale adds an absolute zero, allowing meaningful ratios.

Nominal data only classify, as with gender, religion or blood group.

On a nominal scale only the mode and frequency counts are meaningful.