100 Irregular Plural Nouns in English with Examples

Learning singular and plural nouns is an important part of English grammar. Generally, we form the plural of a noun by adding -s or -es to the singular form. For example, book becomes books and box becomes boxes.

However, some nouns do not follow these regular rules. They form their plurals by changing their spelling, using a different ending, or sometimes keeping the same form. These nouns are called irregular plural nouns.

In this article, you will learn 100 irregular plural nouns in English with examples. This list will help students improve their vocabulary, grammar, reading, and writing skills.

What Are Irregular Plural Nouns?

Irregular plural nouns are nouns that do not form their plurals by simply adding -s or -es.

Examples:

• Man – Men
• Woman – Women
• Child – Children
• Tooth – Teeth
• Mouse – Mice

Let us learn 100 irregular plural nouns with their meanings and example sentences.

1. Irregular Plural Nouns That Change Their Vowels

In some nouns, the vowel sound or spelling changes when we form the plural.

No.	Singular	Plural	Example Sentence
1	Man	Men	Three men are standing outside.
2	Woman	Women	The women are working in the garden.
3	Foot	Feet	My feet are tired after walking.
4	Tooth	Teeth	Brush your teeth twice a day.
5	Goose	Geese	The geese are swimming in the pond.
6	Mouse	Mice	The mice ran under the table.
7	Louse	Lice	Lice can live in human hair.
8	Die	Dice	The children are playing with two dice.

2. Irregular Plural Nouns That Add Special Endings

Some nouns form their plurals by adding special endings rather than simply adding -s or -es.

No.	Singular	Plural	Example Sentence
9	Child	Children	The children are playing in the park.
10	Ox	Oxen	The oxen are pulling a cart.
11	Brother	Brethren	The brethren gathered for the meeting.
12	Penny	Pence	The price was five pence.

Note: Brethren is mainly used in religious or formal contexts. The ordinary plural of brother is brothers. The plural pence is used for amounts of money in British English, while pennies can refer to individual coins.

3. Nouns Borrowed from Latin and Greek

Many English nouns come from Latin or Greek. Some of these nouns retain their traditional plural forms.

No.	Singular	Plural	Example Sentence
13	Analysis	Analyses	The students conducted two analyses.
14	Basis	Bases	These ideas form the bases of our plan.
15	Crisis	Crises	The country faced several crises.
16	Thesis	Theses	The university received the students' theses.
17	Diagnosis	Diagnoses	The doctor reviewed the diagnoses.
18	Hypothesis	Hypotheses	The scientists tested their hypotheses.
19	Parenthesis	Parentheses	Put the extra information in parentheses.
20	Synthesis	Syntheses	The report contains two different syntheses.
21	Ellipsis	Ellipses	The editor corrected the ellipses in the text.
22	Axis	Axes	The graph has two axes.
23	Index	Indices	The mathematical indices are different.
24	Matrix	Matrices	The students solved two matrices problems.
25	Vertex	Vertices	A triangle has three vertices.
26	Appendix	Appendices	The report includes two appendices.
27	Fungus	Fungi	Some fungi grow on decaying wood.
28	Nucleus	Nuclei	The cells contain visible nuclei.
29	Radius	Radii	The circles have different radii.
30	Alumnus	Alumni	The alumni attended the reunion.
31	Alumna	Alumnae	The alumnae organised the event.
32	Curriculum	Curricula	The schools follow different curricula.
33	Syllabus	Syllabuses	The teachers reviewed the syllabuses.
34	Bacterium	Bacteria	Bacteria can be found in many environments.
35	Datum	Data	The data are useful for the study.
36	Medium	Media	Social media influence communication.
37	Memorandum	Memoranda	The office received two memoranda.
38	Stratum	Strata	The rock contains several strata.
39	Phenomenon	Phenomena	Rainbows are beautiful natural phenomena.
40	Criterion	Criteria	Honesty is an important criterion for selection.
41	Genus	Genera	Scientists classify organisms into genera.
42	Species	Species	Several species live in this forest.
43	Formula	Formulae	The students learnt several mathematical formulae.
44	Larva	Larvae	The larvae developed into adult insects.
45	Alga	Algae	Algae grow in ponds and lakes.
46	Amoeba	Amoebae	Amoebae are single-celled organisms.
47	Vertebra	Vertebrae	The spine consists of several vertebrae.
48	Nebula	Nebulae	Astronomers study distant nebulae.
49	Antenna	Antennae	The insects moved their antennae.
50	Oasis	Oases	Travellers found water at the oases.

Important: Some of these nouns also have regular plural forms. For example, funguses, indexes, appendixes, formulas, and syllabuses are acceptable in appropriate contexts. The choice depends on the word and its usage.

4. Nouns Ending in -f or -fe

Some nouns ending in -f or -fe change these endings to -ves in the plural.

No.	Singular	Plural	Example Sentence
51	Leaf	Leaves	The leaves are falling from the trees.
52	Knife	Knives	The knives are in the kitchen drawer.
53	Wife	Wives	The wives attended the celebration.
54	Life	Lives	Many lives were saved by the rescue team.
55	Wolf	Wolves	Wolves live in groups in the wild.
56	Calf	Calves	The calves are grazing in the field.
57	Half	Halves	Cut the apple into two halves.
58	Loaf	Loaves	The baker prepared five loaves of bread.
59	Shelf	Shelves	The books are arranged on the shelves.
60	Thief	Thieves	The police caught the thieves.
61	Elf	Elves	The story is about magical elves.
62	Hoof	Hooves	The horses have strong hooves.
63	Scarf	Scarves	She bought two colourful scarves.
64	Self	Selves	The children wrote about their future selves.
65	Sheaf	Sheaves	The farmer collected sheaves of wheat.

Remember: Not all nouns ending in -f or -fe follow this rule. For example, roof becomes roofs, chief becomes chiefs, and belief becomes beliefs.

5. Nouns That Have the Same Singular and Plural Forms

Some nouns remain unchanged in the plural. Their singular or plural meaning becomes clear from the sentence.

No.	Singular	Plural	Example Sentence
66	Sheep	Sheep	Ten sheep are grazing in the field.
67	Deer	Deer	We saw five deer in the forest.
68	Fish	Fish	There are many fish in the pond.
69	Species	Species	Many species live in the ocean.
70	Series	Series	Two television series are popular.
71	Aircraft	Aircraft	Three aircraft landed at the airport.
72	Spacecraft	Spacecraft	The spacecraft are ready for launch.
73	Salmon	Salmon	Several salmon swim upstream.
74	Trout	Trout	The lake contains many trout.
75	Bison	Bison	A herd of bison crossed the plain.
76	Moose	Moose	We spotted two moose near the lake.
77	Swine	Swine	The farm raises swine.
78	Offspring	Offspring	The birds protect their offspring.
79	Headquarters	Headquarters	The company's headquarters are in Delhi.
80	Means	Means	Several means of transport are available.

Note: The word fish is usually unchanged in the plural, although fishes is also used, particularly when referring to different species. Similarly, people is the usual plural of person, while persons is used in some formal or legal contexts.

6. Other Important Irregular and Special Plural Nouns

The following words are also useful for students. Some have alternative plural forms, while others have special meanings or usage patterns.

No.	Singular	Plural	Example Sentence
81	Person	People	Many people attended the meeting.
82	Brother	Brothers	My brothers live in different cities.
83	Cactus	Cacti	The garden has several cacti.
84	Focus	Foci	The diagram shows two foci.
85	Octopus	Octopuses	We saw two octopuses in the aquarium.
86	Hippopotamus	Hippopotamuses	Hippopotamuses live in Africa.
87	Virus	Viruses	Several viruses can cause illness.
88	Formula	Formulas	The textbook contains useful formulas.
89	Index	Indexes	The book has indexes for different subjects.
90	Appendix	Appendixes	The book includes two appendixes.
91	Stadium	Stadiums	The city has two large stadiums.
92	Aquarium	Aquariums	The school has two aquariums.
93	Bureau	Bureaus	Several government bureaus issued reports.
94	Cherub	Cherubs	The painting shows two cherubs.
95	Seraph	Seraphim	The text mentions seraphim.
96	Manservant	Menservants	The old story mentions two menservants.
97	Woman doctor	Women doctors	Women doctors treated the patients.
98	Policeman	Policemen	The policemen controlled the traffic.
99	Fireman	Firemen	The firemen rescued the family.
100	Salesman	Salesmen	The salesmen visited the shops.

Note: In modern English, gender-neutral alternatives are often preferred, such as police officer, firefighter, and salesperson. Their plurals are police officers, firefighters, and salespeople.

Also, stadiums, aquariums, and bureaus form regular plurals. They are included here as additional vocabulary practice, not as strict examples of irregular plurals.

Important Rules for Forming Irregular Plurals

Remember these common patterns:

Rule 1: Change the vowel.

• Man → Men
• Woman → Women
• Foot → Feet
• Tooth → Teeth
• Mouse → Mice

Rule 2: Add a special ending.

• Child → Children
• Ox → Oxen

Rule 3: Change -f or -fe to -ves in certain words.

• Leaf → Leaves
• Knife → Knives
• Life → Lives
• Wolf → Wolves

Rule 4: Use traditional Latin or Greek plural forms.

• Analysis → Analyses
• Criterion → Criteria
• Phenomenon → Phenomena
• Bacterium → Bacteria

Rule 5: Keep the same form.

• Sheep → Sheep
• Deer → Deer
• Aircraft → Aircraft
• Species → Species

Exercise: Change the Singular Nouns into Plural Nouns

Fill in the blanks with the correct plural forms.

1. There are five ______ in the room. (child)
2. The farmer has ten ______. (sheep)
3. The doctor examined my ______. (tooth)
4. Two ______ are playing in the garden. (woman)
5. The cat chased the ______. (mouse)
6. The farmer has two ______. (ox)
7. The tree has many green ______. (leaf)
8. The scientists studied different natural ______. (phenomenon)
9. The students discussed several ______. (hypothesis)
10. We saw three ______ near the river. (deer)
11. The company has two main ______. (headquarters)
12. The teacher explained the selection ______. (criterion)
13. The baker made several ______ of bread. (loaf)
14. The school follows different ______. (curriculum)
15. The police caught the ______. (thief)

Answers

1. Children
2. Sheep
3. Teeth
4. Women
5. Mice
6. Oxen
7. Leaves
8. Phenomena
9. Hypotheses
10. Deer
11. Headquarters
12. Criteria
13. Loaves
14. Curricula
15. Thieves

Conclusion

Irregular plural nouns are an important part of English grammar. Although many English nouns form their plurals by adding -s or -es, others follow special patterns that students must learn through reading, writing, and practice.

Learning these 100 nouns will help students improve their grammatical accuracy and use English more confidently.

Keep learning, keep practising, and keep enriching your English!