Irregular Plural Nouns in English

Irregular plural nouns can be tricky because they don’t follow the standard rule of adding an “s” or “es” to the end of the singular form. These nouns have unique spellings and can be challenging to master.

In this reference, you will learn what irregular plural nouns are and how to form them. You’ll see examples, common patterns, and tips for identifying and using these nouns correctly. Let’s dive into the world of irregular plural nouns together!

What Are Irregular Plural Nouns?

Irregular plural nouns do not follow the standard rule of adding -s or -es to form their plural version. These nouns are common in English and often require memorization.

Examples of irregular nouns in singular and plural format:

To use irregular plural nouns correctly, you will need to study and memorize them. Searching for the correct plural forms in the dictionary can also help. Without learning these forms, you might make mistakes when using irregular nouns.

Irregular Plural Nouns | Rules

No Change in the Plural

Some nouns have the same singular and plural forms. Many times, these are names of animals.

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

Changing the Spelling of the Singular Noun

The plural form can be made by altering the vowel sound of the singular noun. These are sometimes called mutated plurals.

• 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: Compounds with man and woman follow the same pattern: postmen, policewomen, and others.

Irregular Plural Nouns from Latin and Greek

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

• Alumna – alumnae
• Formula – formulae/formulas
• Antenna – antennae/antennas

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

• 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, -era, -ora or just adds -es

• 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 stays the same

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

Final on becomes -a

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

Final as changes to -antes

• Atlas – Atlantes

Final ma becomes -mata or -s

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

Irregular Plural Nouns from Other Languages

Nouns of French origin

Some nouns of French origin add an -x:

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

Nouns of Slavic origin

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

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

Nouns of Japanese origin

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

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

Other Languages

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

Frequently Misused Irregular Plural Nouns

Man / Men and Woman / Women: One common mistake is using mans or womans as plural forms. The correct plurals are men and women.

Child / Children: The plural of child is not childs but children.

Mouse / Mice and Goose / Geese: Remember that the plural of mouse is mice, and the plural of goose is geese.

Tooth / Teeth and Foot / Feet: These nouns have plurals that are quite different from their singular forms. The correct plurals are teeth and feet, not tooths and foots.

Person / People: The irregular plural form is people. Note that persons is used in legal contexts or specific situations involving a small number of individuals.

Here is a list of some other irregular plural nouns frequently misused:

Avoiding these common mistakes will help improve your writing and speaking accuracy.

Irregular Plural Nouns Video