Category:English invariant nouns

A few English nouns do not change when inflected into the plural. These are known as "invariant nouns" (or "invariable nouns").

Note: These are not to be confused with pluralia tantum (such as bagpipes) or with uncountable nouns (also known as mass nouns and non-count nouns; invariant nouns can still be counted as in "one sheep, two sheep").

A related class are certain possessives that are (headless) elliptical noun phrases. (The chemist's is closed on Sundays. The chemist's were closed on Sundays.) See Appendix:Special uses of possessives in English.

Invariant use of non-invariant nouns
Sometimes in English, the singular form of a non-invariant noun may be used to denote a plural. This should be carefully distinguished from true invariants, where there is no plural form, as in the case of 'sheep'.

Generally, this happens with only a very few kinds of nouns:


 * game animals commonly found in herds or flocks
 * elephant, buffalo, antelope, duck


 * munitions or armaments
 * cannon, rifle


 * measurements
 * inch, millimetre, foot, year, pound