Nominal number

Definition · applies to numbers

Elementary

A nominal number is a number used as a name or label, not to count or to order.

Examples

Examples

• A phone number Elementary
• The “23” on a jersey Elementary
  The “23” on a jersey is a nominal number because it is only a label.

Non-examples

Things that may be mistaken for examples.

• The “3” in “3 apples” Elementary
  The “3” in “3 apples” is not a nominal number, because it is not just a label.
• The “3rd” in “finished 3rd” Elementary
  The “3rd” in “finished 3rd” is not a nominal number, because its order matters.

Notes

Arithmetic on nominal numbers is meaningless: the sum of two ZIP codes is not a ZIP code of anything.

Distinctions involving this term

• Cardinal vs. ordinal vs. nominal numbers: The same numeral, such as “3,” can play different roles in everyday language. A number can be used to count (cardinal), to give a position in an order (ordinal), or as a label (nominal). For finite sets, cardinals and ordinals look the same, but for infinite sets they differ.

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