Irregular plural nouns are nouns that do not follow the standard rule of adding “-s” or “-es” to form the plural. Instead, they change in different ways, such as changing vowels (man → men), adding “-ves” (leaf → leaves), or staying the same (sheep → sheep). These irregular forms can be confusing for English learners, but mastering them will improve your grammar and fluency in both spoken and written English.
In this article, we’ll explore different types of irregular plural nouns, provide common examples with sentences, and help you avoid common mistakes. At the end, test your knowledge with a 10-question quiz!
Types of Irregular Plural Nouns
1. Changing the Vowel
Some nouns change the vowel sound in the plural form:
Singular Plural Example Sentence
Man Men There are ten men in the room.
Woman Women The company hired five women.
Foot Feet My feet hurt after walking all day.
Tooth Teeth I have two missing teeth.
Goose Geese We saw a flock of geese by the lake.
2. Changing “-f” or “-fe” to “-ves”
Some nouns ending in “-f” or “-fe” change to “-ves” in the plural:
Singular Plural Example Sentence
Wolf Wolves There are many wolves in the forest.
Leaf Leaves The tree’s leaves turned yellow.
Knife Knives Be careful with sharp knives.
Life Lives Many lives were saved by the doctor.
Wife Wives The two men talked about their wives.
3. Changing to a Completely Different Word
Some words completely change in the plural form:
Singular Plural Example Sentence
Child Children The school is full of children.
Person People Many people came to the event.
Mouse Mice We saw three mice in the kitchen.
Louse Lice The child had lice in his hair.
Die Dice He rolled the dice in the game.
4. Staying the Same
Some nouns do not change at all in the plural form:
Singular Plural Example Sentence
Sheep Sheep There are five sheep in the field.
Deer Deer We saw three deer in the forest.
Fish Fish I caught two fish in the river.
Moose Moose A moose crossed the road.
Aircraft Aircraft The aircraft is ready for takeoff.
Note: Some people use “fishes” when referring to different species of fish.
5. Foreign Words That Follow Their Original Language Rule
Some nouns borrowed from Latin, Greek, and other languages keep their original plural forms:
Singular Plural Example Sentence
Cactus Cacti The desert has many cacti.
Radius Radii The scientist measured the radii of the circles.
Datum Data The research is based on data.
Medium Media Social media is very popular.
Crisis Crises The country faced two economic crises.
Exceptions & Special Cases
Some nouns have two correct plural forms:
- Octopus → Octopuses / Octopi (Both are correct.)
- Cactus → Cactuses / Cacti (Both are used.)
- Focus → Focuses / Foci (Scientific use prefers “foci.”)
Some nouns look plural but are singular:
- News → The news is important.
- Mathematics → Mathematics is difficult.
- Physics → Physics is my favorite subject.
Some nouns look singular but are plural:
- Scissors → The scissors are sharp.
- Glasses → My glasses are broken.
- Trousers → His trousers are new.
Irregular Plural Nouns – Quiz
1. What is the correct plural of “child”?
a) Childs
b) Childrens
c) Children
2. Which sentence is correct?
a) My foots hurt.
b) My feet hurt.
c) My feets hurt.
3. What is the plural of “person”?
a) People
b) Persons
c) Peoples
4. “There are many ___ in the forest.” (deer)
a) Deers
b) Deer
c) Deeres
5. The plural of “tooth” is:
a) Tooths
b) Teeth
c) Teeths
6. Which sentence is correct?
a) I have two knifes.
b) I have two knives.
c) I have two knivies.
7. What is the plural of “mouse”?
a) Mouses
b) Mices
c) Mice
8. The plural of “crisis” is:
a) Crisises
b) Crises
c) Crisis
9. “The ___ are flying in the sky.” (aircraft)
a) Aircraft
b) Aircrafts
c) Aircrafs
10. What is the correct plural of “goose”?
a) Gooses
b) Geese
c) Goose
Quiz Answers
1) Children
2) My feet hurt.
3) People
4) Deer
5) Teeth
6) I have two knives.
7) Mice
8) Crises
9) Aircraft
10) Geese