Irregular Plural Nouns in English

Irregular Plural Nouns in English

Prototypical English nouns have both singular and plural forms. Singular nouns refer to one “person, place, thing, or idea” while plural nouns refer to “not one” (two or more or less than one) “people, places, things, or ideas.” Regular nouns are predictable, taking an -s suffix to form the plural. Irregular nouns are unpredictable, following other rules to form the plural. Learn how to form the plural forms of irregular English nouns with the following guide.

Forming Irregular Plural Nouns

Unlike most English nouns through which -s or ­-es suffixation creates the plural forms, irregular English nouns require different changes from the singular to the plural. Some irregular English nouns require a vowel sound change, or ablaut, between the singular and plural forms. For example:

  • foot – feet
  • goose – geese
  • louse – lice
  • man – men
  • mouse – mice
  • person – people (vowel and consonant sound changes)
  • tooth – teeth
  • woman – women

Some irregular nouns in English are formed by the addition of an -en suffix. For example:

  • child – children
  • ox – oxen
  • hose – hosen (archaic)
  • brother – brethren (archaic)

For other irregular English nouns, the plural form is identical to the singular form. For example:

  • bison
  • deer
  • fish
  • moose
  • offspring
  • sheep

Forming Foreign Loanword Plurals

Many loanwords from foreign languages have irregular plural forms. For Latin loanwords that end in a, change the a to an ae. For example:

  • alumna – alumnae
  • formula – formulae

For Latin loanwords that end in ex or ix, change the ex or ix to ices. For example:

  • index – indices/indexes
  • matrix – matrices
  • vertex – vertices

For Latin loanwords that end in is, change the is to an es. For example:

  • analysis – analyses
  • axis – axes
  • crisis – crises
  • testis – testes
  • thesis – theses

For Latin loanwords that end in on, change the on to an a. For example:

  • automaton – automata
  • criterion – criteria
  • phenomenon – phenomena

For Latin loanwords that end in um, change the um to an a. For example:

  • addendum – addenda
  • datum – data
  • medium – media
  • memorandum – memoranda
  • millennium – millennia

For Latin loanwords that end in us, change the us to an i, era, ora, or es. For example:

  • alumnus – alumni
  • cactus – cacti
  • corpus – corpora
  • census – censuses
  • focus – foci
  • fungus – fungi
  • genus – genera
  • radius – radii
  • syllabus – syllabi
  • uterus – uteri
  • viscus – viscera

For Greek loanwords that end in ma, add the suffix -ta to the end of the word. For example:

  • dogma – dogmata
  • schema – schemata
  • stigma – stigmata
  • stoma – stomata

For some French loanwords that end in eau, add a silent -x suffix to the end of the word. For example:

  • beau – beaux
  • bureau – bureaux/bureaus
  • château – châteaux

For some Hebrew loanwords, add the suffix -im or -ot to the end of the word. For example:

  • cherub – cherubim
  • matzah – matzot
  • seraph – seraphim

Irregular English nouns regular either stem changes or ending changes (or sometimes both) in the plural. Loanwords from foreign languages also often have irregular plural forms depending on the language from which the noun was borrowed.

Learn about forming the plurals of regular English nouns in Regular Plural Nouns in English.

See also Plural English Nouns for a printable that lists the rules for forming plurals of regular, irregular, and foreign loanword nouns in the English language with examples.


Hopper, Paul J. 1999. A short course in grammar. New York: W. W. Norton & Company.
Huddleston, Rodney. 1984. Introduction to the grammar of English. Cambridge: Cambridge University Press.

Written by Heather

Heather is a writer, librarian, linguist, wife, homemaker, homeschooler, and mother.

Regular Plural Nouns in English

Regular Plural Nouns in English

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