Irregular Nouns with Example Sentences

What irregular nouns are

Most English nouns form the plural by adding -s or -es: book becomes books, and box becomes boxes. An irregular noun does not follow this pattern. The plural may change inside the word (foot, feet), take an unusual ending (child, children), stay the same (sheep), or follow a rule borrowed from Latin or Greek (criterion, criteria).

Irregular plurals are mostly learned word by word, but many fit into a few patterns, and seeing them in sentences helps.

Ten common irregular plurals with example sentences

If you are looking for ten examples to start with, these are all very common.

Patterns to learn

Vowel changes

The vowel sound or spelling changes: man/men, woman/women, foot/feet, tooth/teeth, goose/geese, mouse/mice, louse/lice.

• The geese flew over the lake.

The -en ending

A small group takes -en or -ren: child/children, ox/oxen.

• The farmer owned two oxen.

Nouns ending in -f or -fe that change to -ves

Several nouns ending in -f or -fe change to -ves in the plural: knife/knives, wife/wives, life/lives, leaf/leaves, wolf/wolves, shelf/shelves, loaf/loaves, half/halves, thief/thieves, calf/calves, elf/elves and self/selves.

• The thieves ran away before the police arrived.
• We cut the cake into halves.

This is not a rule for every noun ending in -f. Many simply add -s: roof/roofs, chief/chiefs, belief/beliefs, cliff/cliffs. A few words accept two forms, such as scarves or scarfs, so check a dictionary if you are unsure.

Same form in singular and plural

Sheep, deer, species, series, aircraft and moose do not change. The verb and the context show whether they are singular or plural.

• A deer was standing near the road. / Three deer were standing near the road.

Fish usually stays the same too. The form fishes is sometimes used when talking about different kinds of fish, but this use is less common.

Latin and Greek nouns

Some nouns from Latin or Greek keep their original plural forms, especially in academic or scientific writing.

Some of these also have an English-style plural. For example, cactus can be cacti or cactuses, and appendix can be appendices or appendixes. The Latin-style form is often preferred in formal writing, but usage varies, so a good dictionary is the best guide. Data was originally the plural of datum. In current English it is used with both singular and plural verbs depending on the context and the style guide you follow.

Nouns that are usually plural only

Some nouns are normally used in the plural form with no singular: scissors, trousers, glasses (for eyes), clothes. We often say “a pair of scissors” for one item.

• These trousers are too long.

Is “children” an irregular noun?

Yes. Children is the irregular plural of child. The regular pattern would be “childs”, which is not used in standard English. Because children already shows plural, you do not add another -s.

Irregular possessive nouns

Possessives with irregular plurals follow one simple pattern: if the plural does not end in -s, add apostrophe plus s.

• the children’s toys
• the men’s team
• the women’s coats
• the people’s opinion

If the plural already ends in -s, add only the apostrophe: the dogs’ bowls (more than one dog). Compare this with the dog’s bowl (one dog).

Exercise 1: write the plural

Write the plural of each noun.

1. child
2. tooth
3. knife
4. sheep
5. woman
6. mouse
7. analysis
8. criterion
9. leaf
10. wife

Exercise 2: complete the sentence

Write the plural form of the word in brackets.

1. Both ___ (woman) arrived late.
2. She washed the ___ (knife) and put them away.
3. There are three ___ (sheep) in the field.
4. My ___ (foot) hurt after the long walk.
5. The scientists tested two ___ (hypothesis).
6. Many ___ (person) waited outside the shop.

Exercise 3: write the possessive

Rewrite each phrase using a possessive form.

1. the toys of the children
2. the hats of the men
3. the opinion of the people
4. the bowls of the two dogs
5. the coats of the women

Exercise 4: correct the mistake

Each sentence has one incorrect plural. Rewrite it correctly.

1. The childs are in the garden.
2. Two mouses ran across the floor.
3. The thiefs ran away.
4. She lost three tooths.
5. There are many sheeps on the hill.

Answer key

Exercise 1: 1. children. 2. teeth. 3. knives. 4. sheep. 5. women. 6. mice. 7. analyses. 8. criteria. 9. leaves. 10. wives.

Exercise 2: 1. women. 2. knives. 3. sheep. 4. feet. 5. hypotheses. 6. people.

Exercise 3: 1. the children’s toys. 2. the men’s hats. 3. the people’s opinion. 4. the two dogs’ bowls. 5. the women’s coats.

Exercise 4: 1. The children are in the garden. 2. Two mice ran across the floor. 3. The thieves ran away. 4. She lost three teeth. 5. There are many sheep on the hill.

Tips for learning irregular nouns

• Learn them in groups. Study the vowel-change nouns together, then the -ves nouns.
• Say them aloud. The sound of feet or mice often sticks better than the spelling alone.
• Learn singular and plural as a pair. Write “tooth, teeth” in your notebook.
• Notice them in reading. Irregular plurals appear often in news and science writing; our list of best input sources for language learners suggests where to find reading material.
• Check a dictionary for rare ones. Dictionaries show the plural next to the headword when it is irregular.

Related practice

Plural forms are one example of how word endings work in English. Our suffixes exercises cover other endings that build nouns, adjectives, adverbs and verbs.