What irregular nouns are
Most English nouns form the plural by adding -s or -es: cat/cats, box/boxes. An irregular noun is one whose plural does not follow that pattern, such as man/men or mouse/mice. Irregular plurals usually have to be learned individually, but they fall into a handful of patterns that make them easier to remember.
Vowel change
Some nouns change an internal vowel (or vowels) to become plural.
| Singular | Plural |
|---|---|
| man | men |
| woman | women |
| foot | feet |
| tooth | teeth |
| goose | geese |
| mouse | mice |
| louse | lice |
Example sentences:
- Two men carried the sofa upstairs.
- My feet hurt after the long walk.
- The geese flew south in a neat line.
- We set traps because there were mice in the garage.
-en and -ren endings
A few nouns take an -en ending, and one takes -ren.
- ox becomes oxen
- child becomes children
Is “children” an irregular noun? Yes. The plural of child is children, not childs, so it counts as irregular. The -ren ending is a historical form, not a general rule.
- The farmer harnessed two oxen to the plow.
- The children played in the yard.
Nouns ending in -f or -fe: the -ves pattern
Many nouns that end in -f or -fe change that ending to -ves.
| Singular | Plural |
|---|---|
| knife | knives |
| life | lives |
| wife | wives |
| leaf | leaves |
| wolf | wolves |
| half | halves |
| shelf | shelves |
| thief | thieves |
| loaf | loaves |
| calf | calves |
| self | selves |
| elf | elves |
- She sharpened the knives before dinner.
- The leaves turn gold in October.
- Wolves hunt in packs.
Exceptions. Not every noun ending in -f works this way. Many simply add -s: roof/roofs, chief/chiefs, belief/beliefs, cliff/cliffs. A few accept two forms, such as hoof (hoofs or hooves) and scarf (scarfs or scarves). When in doubt, check a dictionary.
Unchanged plurals
Some nouns have the same form in the singular and the plural.
- sheep
- deer
- moose
- series
- species
- aircraft
Context tells you whether the word is singular or plural:
- One sheep is standing alone. Fifty sheep are in the next field.
- This species is rare, but several species live in the lake.
“Fish” is usually unchanged too (We caught six fish), though fishes is sometimes used for different kinds of fish.
Latin and Greek plurals
Some words borrowed from Latin or Greek keep their original plural endings.
| Singular | Plural |
|---|---|
| analysis | analyses |
| crisis | crises |
| phenomenon | phenomena |
| criterion | criteria |
| bacterium | bacteria |
| alumnus | alumni |
| cactus | cacti (or cactuses) |
| appendix | appendices (or appendixes) |
- The doctor ordered several analyses of the blood sample.
- Many different phenomena can be explained by the same theory.
- The college invited its alumni to the reunion.
Some of these also have an English-style plural in everyday use, so both forms may be accepted. A few, like data, are used as a plural or as a mass noun depending on the style guide.
Plural-only nouns
Certain nouns usually appear only in the plural form: scissors, trousers, glasses, pliers. They take plural verbs (a point tested in sentence correction exercises), and to talk about one item people often say “a pair of”.
- My scissors are on the desk.
- She bought a pair of trousers.
Irregular possessives
What are irregular possessive nouns? They are possessives built from irregular plurals. A regular plural ending in -s takes only an apostrophe (the dogs’ bowls). An irregular plural that does not end in -s takes apostrophe plus s. (For the wider rules on apostrophes, see the importance of punctuation.)
| Plural | Possessive |
|---|---|
| children | children’s |
| men | men’s |
| women | women’s |
| people | people’s |
| mice | mice’s |
- The children’s books are on the lower shelf.
- The men’s team won the final.
- The people’s voices carried across the square.
Compare the boys’ room (regular plural) with the children’s room (irregular plural).
Ten example sentences
- The women gathered for the meeting.
- Several teeth were loose.
- Both wives attended the ceremony.
- The shelves were full of old books.
- Two deer crossed the road.
- The criteria for the prize are listed online.
- All the crises were resolved by evening.
- The oxen pulled the cart slowly.
- Mice can squeeze through tiny gaps.
- The children’s laughter echoed down the hall.
Tips for remembering
- Learn irregular plurals in groups, as in the sections above, rather than one at a time.
- Say pairs aloud (foot, feet; goose, geese).
- Write short sentences using each form.
- Check any plural you are unsure about in a dictionary, since some words accept two forms.
For other noun-related skills, our article on why compound words matter explains how many nouns are built, and our guide to indefinite adjectives shows how words like many and few pair with plural nouns.
Summary
Irregular nouns break the add-s rule, but most fit a pattern: vowel change, -en/-ren, -ves, unchanged forms, or Latin and Greek endings. For possessives, add apostrophe plus s when the plural does not end in s.