Irregular plural nouns

Many English nouns have irregular plural forms. While the general rule says that adding -s or -es to a noun forms its plural, this is not always true. The following examples show some of the ways English nouns become plural.

For some nouns, like fish, there is no difference between the singular form and the plural form. Sometimes, however, people do use regular plural endings for irregular nouns, so in casual conversation you may hear fishes or elks. 

One fish; three fish

A deer; many deer

An elk; some elk

One species; several species

A series; many series

Some English words come from Latin, and take a Latinate plural ending.

A syllabus; all of the syllabi

A larva; many larvae

This genus; these genera

Her thesis; their theses

One crisis; two crises

An index; a couple of indices

A matrix; two matrices

Sometimes nouns end in -f or -fe and the f becomes a v before adding -s or -es.

A loaf of bread; a few loaves of bread

One wolf; a pack of wolves

A knife; some knives

Some plurals have no pattern and have to be memorized.

That person; those people

نکته: در موتون رسمی و حقوقی از (persons) استفاده می کنیم، برای تفکیک بین چند فرد و یا گروهی از افراد. 

One child; three children

One mouse; two mice

A goose; several geese

A man; two men

An ox; a pair of oxen

Some nouns do not have plural forms because they cannot be counted. These are called noncount nouns, or mass nouns. Some common noncount nouns are water, rice, sand, butter, mud, rain, advice, homework, progress, and music.

Here is a full list of some the most common irregular plural nouns in English:

Child/Children

Man/Men

Woman/Women

Person/People

Persons is often used in formal, legal contexts to emphasize individuals as opposed to a group. People is the plural of person that's most commonly used in everyday communication to simply refer to multiple humans. But people can also be used as a singular noun to refer to a population or particular community.

Mouse/Mice

Goose/Geese

Foot/Feet

Tooth/Teeth

Fungus/Fungi

Cactus/Cacti

Sheep/Sheep

Fish/Fish

Deer/Deer

Moose/Moose

Crisis/Crises

Wolf/Wolves

Index/Indices

Ox/Oxen

Analysis/Analyses

Basis/Bases

Diagnosis/Diagnoses

Hypothesis/Hypotheses

Oasis/Oases

Synthesis/Syntheses

Thesis/Theses

Axis/Axes

Appendix/Appendices

Nucleus/Nuclei

Focus/Foci             

Matrix /Matrices

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Irregular plural nouns examples in sentences

Here are some examples of irregular plural nouns used in sentences:

There were two mice scurrying around the kitchen.

Both children were playing in the park.

She saw a herd of deer in the forest.

The men were discussing the issue.

He saw a flock of geese flying in the sky.

The people of the town gathered for the meeting.

There were several cacti in the garden.

Rules of irregular plurals

Although there are no hard rules for forming irregular plural nouns, there are some patterns that can help you remember them.

Some nouns just change one letter, such as 'man' to ‘men,’ or ‘woman’ to 'women.'

Some nouns change their spelling completely, such as 'mouse' to 'mice'.

Some nouns use the same form in both singular and plural, such as 'sheep' and 'fish'.

Some nouns have a different ending depending on their origin, such as 'fungus' to 'fungi'.

Once you find and remember enough of these words, you will be able to remember the correct plural form of most irregular nouns based on these patterns.

Common mistakes

One of the most common mistakes that English learners make with irregular plural nouns is confusing them with regular nouns. The plural of 'man' is 'men' and not 'mans'. Similarly, the plural of 'woman' is 'women' and not 'womans'.

Similarly, the plural of 'person' is 'people' and not 'persons' although this form sometimes comes up when we refer to a number of individuals. Remember that some nouns share the same form in both singular and plural, such as 'sheep' and 'fish'.

100 Irregular Plural Nouns List

In the list below, you'll find singular noun forms in the left column and the corresponding plural forms in the right column. When a noun has more than one plural form, the irregular one appears first, though that doesn't necessarily mean that the irregular form is more widely accepted than the regular form.

addendum addenda or addendums

aircraft aircraft

alumna alumnae

alumnus alumni

analysis analyses

antenna antennae or antennas

antithesis antitheses

apex apices or apexes

appendix appendices or appendixes

axis axes

bacillus bacilli

bacterium bacteria

basis bases

beau beaux or beaus

bison bison

bureau bureaux or bureaus

cactus cacti or cactus or cactuses

château châteaux or châteaus

child children

codex codices

concerto concerti or concertos

corpus corpora

crisis crises

criterion criteria or criterions

curriculum curricula or curriculums

datum data

deer deer or deers

diagnosis diagnoses

die dice or dies

dwarf dwarves or dwarfs

ellipsis ellipses

erratum errata

faux pas faux pas

fez fezzes or fezes

fish fish or fishes

focus foci or focuses

foot feet or foot

formula formulae or formulas

fungus fungi or funguses

genus genera or genuses

goose geese

graffito graffiti

grouse grouse or grouses

half halves

hoof hooves or hoofs

hypothesis hypotheses

index indices or indexes

larva larvae or larvas

libretto libretti or librettos

loaf loaves

locus loci

louse lice

man men

matrix matrices or matrixes

medium media or mediums

memorandum memoranda or memorandums

minutia minutiae

moose moose

mouse mice

nebula nebulae or nebulas

nucleus nuclei or nucleuses

oasis oases

offspring offspring or offsprings

opus opera or opuses

ovum ova

ox oxen or ox

parenthesis parentheses

phenomenon phenomena or phenomenons

phylum phyla

quiz quizzes

radius radii or radiuses

referendum referenda or referendums

salmon salmon or salmons

scarf scarves or scarfs

self selves

series series

sheep sheep

shrimp shrimp or shrimps

species species

stimulus stimuli

stratum strata

swine swine

syllabus syllabi or syllabuses

symposium symposia or symposiums

synopsis synopses

tableau tableaux or tableaus

thesis theses

thief thieves

tooth teeth

trout trout or trouts

tuna tuna or tunas

vertebra vertebrae or vertebras

vertex vertices or vertexes

vita vitae

vortex vortices or vortexes

wharf wharves or wharfs

wife wives

wolf wolves

woman women

Irregular Plural Nouns

Learning to use most plural nouns in English is fairly easy. But unfortunately, some common plural nouns in English are irregular. What are these irregular plural nouns, and how can you remember them? Read on to find out!

Regular Plural Nouns

The majority of nouns in English follow the same rule to create plural nouns, and that is to add -s. For example,

A pen / Some pens

A student / Some students

This is true for all words except words that end in -ch, -sh, -s, -ss, -x, -z, and -o. With these words, we add -es. For example,

A watch / Some watches

A tomato / Some tomatoes

And when a word ends in -y, you change the -y to -i and add -es. For example,

A city / Some cities

A lady / Some ladies

Irregular Plural Nouns

There are some plural nouns that don’t follow the rule above of using -s. Here are the irregular plural nouns you need to know.

People

Children (plural of child). “There are some children playing in the park.”

Women (plural of woman), pronounced /’wi min/. “Two of our top managers are women.”

Men (plural of man). “The changing room for the men is over there.”

People (plural of person). “There are over 7.5 billion people in the world.”

Body

Teeth (plural of tooth). “He has perfect teeth. He never has to go to the dentist.”

Feet (plural of foot). “You walk and run with your feet.”

Animals

The following animals have the same plural form as the singular form:

Fish (one fish, two fish)

Sheep

Deer

Shrimp

Tuna

Swine

Species

While some plural nouns for animals change significantly:

A mouse / Some mice

A goose / Some geese

An ox / Some oxen

Words ending in -f

Words that end in -f or -fe change the -f to -v before adding -es. For example,

A life – Some lives

A knife – Some knives

A leaf – Some leaves

A wife – Some wives

A calf – Some calves

A loaf – Some loaves

A scarf – Some scarves

Words ending in -is

Words that end in -is usually change to -es. For example,

A hypothesis / Some hypotheses

A crisis / Some crises

An analysis / Some analyses

A thesis / Some theses

Plural Words ending in -a

The following are all common irregular plural words that end in -a:

Data

Criteria

Phenomena

Media

Bacteria

Curricula