Plural nouns refer to more than one person, animal, or thing. Most English nouns make the plural by adding -s or -es, but irregular plural nouns do not follow that pattern. They show plurality in another way, such as a vowel change, a different ending, or no change at all. In one book, book names a single thing. In two books, books shows more than one. In one man, man is singular. In two men, men is the plural form, even though it does not add -s. The plural form belongs to the whole noun, not to a separate word added after it.

Vowel change plural noun forms

Word	Definition	Example
man	The plural is men, which is the form used for more than one male adult person.	One man is waiting, and two men are outside.
woman	The plural is women, which is the form used for more than one female adult person.	One woman is here, and three women are coming.
tooth	The plural is teeth, which is the form used for more than one tooth.	My tooth hurts, but my teeth are fine.
mouse	The plural is mice, which is the form used for more than one mouse.	I saw one mouse in the kitchen, but the mice ran away.
louse	The plural is lice, which is the form used for more than one louse.	A louse is tiny, and lice can spread quickly.

Scramble

Some irregular plurals change the vowel inside the noun. Man becomes men, and woman becomes women. These forms are learned as complete nouns, not as nouns plus an ending. The change happens in the middle of the word, while the spelling stays close to the singular form. A sentence like The men are waiting outside uses the plural noun because there is more than one man. The women work in the next room does the same for woman. The singular form takes is or a when one person is meant, while the plural form takes plural agreement and plural words such as are or these.

Irregular plural nouns with new endings

Word	Definition	Example
child	The plural is children, which is the form used for more than one child.	One child is sleeping, and the children are awake.
goose	The plural is geese, which is the form used for more than one goose.	A goose is on the lawn, and geese are flying above us.
foot	The plural is feet, which is the form used for more than one foot.	My foot is sore, so my feet need a rest.
person	The plural is people, which is the form used for more than one person.	One person is at the door, and many people are in the hall.
ox	The plural is oxen, which is the form used for more than one ox.	An ox pulls the cart, and oxen can be very strong.

Scramble

Some irregular plurals use a different ending instead of -s. Child becomes children, goose becomes geese, and foot becomes feet. These plurals are not made by adding a regular plural ending to the singular form. They are separate plural words that must be remembered. In a sentence, the plural noun follows the same grammar as other plural nouns: The children are at school, The geese fly south, My feet hurt after the walk. The singular and plural forms are different words, so the meaning changes with the form itself.

Nouns with identical singular and plural forms

Example	Pattern
One sheep is in the field, and five sheep are nearby.	Use the same word for singular and plural when the noun is one of these unchanged forms.
I caught one fish, but we saw many fish in the river.	Some nouns stay the same because the count is shown by the context.
One deer crossed the road, and two deer followed it.	Words like deer do not change, so the article or number tells you the amount.
This series is new, and three series are on the list.	Use the same spelling for series and similar nouns when the singular and plural look alike.

Some nouns have the same form in the singular and the plural. Sheep, fish, and deer do not change form when there is more than one. In one sheep and five sheep, the noun looks the same, so the words around it show the number. A deer is in the yard uses singular meaning because of a and is. Three deer are in the yard uses plural meaning because of three and are. Context gives the number through determiners, numbers, and verb agreement. The noun itself stays unchanged.

Plural determiners with irregular count nouns

Usage	Explanation	Example
Demonstratives	Use these with irregular plural nouns when you point to things that are close.	These children are my neighbors.
Quantifiers	Use many with irregular plural nouns to show a large number.	Many geese flew over the lake.
Small amount	Use some with irregular plural nouns to mean an unspecified number.	I saw some mice in the garage.
Number words	Use exact numbers with irregular plural nouns to count more precisely.	We need two feet of rope.
Countable meaning	Use irregular plural nouns as countable nouns when you can separate them into individual items.	There are three women at the table.

Irregular plural nouns normally work with plural determiners such as these, those, many, several, and some. You say these men, those children, many feet, and some geese. They also combine with numbers: two women, four sheep, ten fish. Because they name separate items that can be counted, they are usually countable nouns. A countable noun can appear in singular or plural form. In the singular, it often needs a determiner such as a or one. In the plural, it can stand with plural words and plural verbs. Words like much usually do not go with these nouns, because much is used with uncountable nouns.

Plural forms inside compound nouns

Example	Pattern
One mother in law visited, and two mothers in law came later.	In many compounds, add the plural ending to the main noun.
A passerby waved, and several passersby smiled back.	When a compound has a clear head noun, make that head noun plural.
One sister in law is here, and three sisters in law are waiting.	Do not change every part of the compound when only one noun carries the plural meaning.
A truck driver arrived, and the truck drivers parked outside.	Some compounds keep the same order, but the central noun changes form.

A compound noun has two or more words that work together as one noun. In many compounds, only the main noun becomes plural. Mother-in-law becomes mothers-in-law, and passerby becomes passersby. The noun that carries the main meaning takes the plural form, while the other words stay the same. In sisters-in-law, the plural mark goes on sister, not on law. In editors-in-chief, the plural mark goes on editor. The plural form appears on the part of the compound that names the person or thing being counted.

Accepted plural variants across usage

Region	Variant	Definition	Example
United States	cactuses	This plural is accepted in modern American English for the plant called cactus.	We saw three cactuses in the garden.
United Kingdom	cacti	This plural is common in careful or formal English for the plant called cactus.	The shop sells small cacti near the window.
United States	fishes	This plural can mean different kinds of fish in some contexts.	The aquarium displays many fishes from the reef.
United Kingdom	species	This word has the same form in singular and plural in standard English.	One species is endangered, and several species live here.
United States	data	This form is often used as a singular mass noun in modern English.	The data show a clear pattern.

Scramble

Some nouns have more than one accepted plural form. Cactus can become cacti or cactuses. Focus can become foci or focuses. In modern English, the regular-style plural is often common in everyday speech, while the Latin or Greek form appears in more formal writing or in certain fields. Some nouns keep the same form in singular and plural, especially words such as species and deer. Fish can also stay the same in many contexts, as in two fish. Sometimes fishes is used when different kinds are being discussed, as in the fishes of the river. The choice depends on the word and the context, but the plural meaning still comes from the noun form and the words around it.