Irregular Plural Nouns: Important Rules, Lists, and Examples

What is an irregular plural noun? Learn important grammar rules related to Irregular Plural Nouns in English with lists, examples, and ESL infographics.

What Are Irregular Plural Nouns?

Irregular plural nouns don’t adhere to specific rules; therefore, it’s prudent to study them or search for accurate pluralization in the dictionary. Lack of definite rules makes it challenging to understand them. So, you must devote your time to study and memorize them. Otherwise, you’re bound to error when making use of irregular nouns in plural form.

Examples of irregular nouns in singular and plural format:

Singular	Plural
Man	Men
Foot	Feet
Mouse	Mice
Child	Children
Woman	Women
Goose	Geese
Person	People

Irregular Plural Nouns | Rules

No Change in the Plural

Some nouns have identical singular and plural. Many of these are the names of animals.

Irregular Plural Nouns List:

• Aircraft – aircraft
• Barracks – barracks
• Deer – deer
• Gallows – gallows
• Moose – moose
• Salmon – salmon
• Hovercraft – hovercraft
• Spacecraft – spacecraft
• Series – series
• Species – species
• Means – means
• Offspring – offspring
• Deer – deer
• Fish – fish
• Sheep – sheep
• Offspring – offspring
• Trout – trout
• Swine – swine

Changing the Spelling of the Singular Noun

The plural is sometimes formed by simply changing the vowel sound of the singular (these are sometimes called mutated plurals):

Irregular Plural Nouns List:

• Person – people
• Ox – oxen
• Man – men
• Woman – women
• Caveman – cavemen
• Policeman – policemen
• Child – children
• Tooth – teeth
• Foot – feet
• Goose – geese
• Mouse – mice
• Louse – lice
• Penny – pence

Note: There are many compounds of man and woman that form their plurals in the same way: postmen, policewomen, etc.

Irregular Nouns – Image 1

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Irregular Plural Nouns from Latin and Greek

Final a becomes -ae (also -æ), or just adds -s

• Alumna – alumnae
• Formula – formulae/formulas

Final ex or ix becomes -ices

• Index – indices /indexes
• Matrix – matrices
• Vertex – vertices
• Appendix – appendices

Final is becomes es

• Axis – axes
• Genesis – geneses
• Nemesis – nemeses
• Crisis – crises
• Testis – testes

Final um becomes -a, or just adds -s

Irregular Plural Nouns List:

• Addendum – addenda
• Corrigendum – corrigenda
• Datum – data
• Forum – fora/forums
• Medium – media/ mediums
• Memorandum – memoranda/memorandums
• Millennium – millennia
• Ovum – ova
• Spectrum – spectra

Final us becomes -i or -era or -ora or just adds -es

Irregular Plural Nouns List:

• Alumnus – alumni
• Corpus – corpora
• Census – censuses
• Focus – foci
• Genus – genera
• Prospectus – prospectuses
• Radius – radii
• Campus – campuses
• Succubus – succubi
• Stylus – styli
• Syllabus – syllabi/syllabuses
• Viscus – viscera
• Virus – viruses/virii
• Cactus – cactuses/cacti
• Fungus – fungi
• Hippopotamus – hippopotamuses/hippopotami
• Octopus – octopuses
• Terminus – termini/terminuses
• Uterus – uteri/uteruses

Final us remains unchanged in the plural

• Meatus – meatus/meatuses
• Status – status/statuses

Final on becomes -a

• Automaton – automata
• Criterion – criteria
• Phenomenon – phenomena
• Polyhedron – polyhedra

Final as in one case changes to -antes

• Atlas – Atlantes (statues of the Titan); but Atlas – atlases (map collections)

Final ma in nouns of Greek origin can become -mata

Final ma in nouns of Greek origin can become -mata, although -s is usually also acceptable, and in many cases more common.

• Stigma – stigmata/stigmas
• Stoma – stomata/stomas
• Schema – schemata/schemas
• Dogma – dogmata/dogmas
• Lemma – lemmata/lemmas
• Anathema – anathemata/anathemas

Irregular Plural Nouns from Other Languages

Some nouns of French origin add an -x:

• Beau – beaux/beaus
• Bureau – bureaux/bureaus
• Tableau – tableaux/tableaus

Nouns of Slavic origin add -a or -i according to native rules, or just -s:

• Kniazhestvo – kniazhestva/kniazhestvos
• Kobzar – kobzari/kobzars
• Oblast – oblasti/oblasts

Nouns of Hebrew origin add -im or -ot (generally m/f) according to native rules, or just -s:

• Cherub – cherubim/cherubs
• Seraph – seraphim/seraphs
• Matzah – matzot/matzahs
• Kibbutz – kibbutzim/kibbutzes

Many nouns of Japanese origin have no plural form and do not change:

• Benshi – benshi
• Otaku – otaku
• Samurai – samurai

Nouns from languages other than the above generally form plurals as if they were native English words:

• Canoe – canoes
• Igloo – igloos
• Kangaroo – kangaroos
• Kayak – kayaks
• Kindergarten – kindergartens
• Pizza – pizzas
• Sauna – saunas
• Ninja – ninjas

Irregular Nouns – Image 2

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Irregular Plural Nouns Videos

Learn more useful rules to form regular plural nouns in English.

Last Updated on July 14, 2022