50 Most Common Irregular Plurals in English – Master These Tricky Nouns!

irregular plurals

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1. Child → Children

• One child, two children.

2. Person → People

• Three people (not "persons" in everyday speech).

3. Man → Men

• One man, five men.

4. Woman → Women

• A woman, three women.

5. Tooth → Teeth

• Brush your teeth.

6. Foot → Feet

• The table is six feet long.

7. Mouse → Mice

• A computer mouse, two mice.

8. Goose → Geese

• A goose, a flock of geese.

9. Ox → Oxen (rare, but classic)

• An ox, a team of oxen.

10. Louse → Lice

• Head lice are contagious.

11. Die → Dice (for gaming)

• Roll the dice.

12. Cactus → Cacti (or "cactuses")

• The desert has many cacti.

13. Fungus → Fungi (or "funguses")

• Mushrooms are fungi.

14. Nucleus → Nuclei (scientific)

• Cell nuclei contain DNA.

15. Syllabus → Syllabi (or "syllabuses")

• Check the course syllabi.

16. Analysis → Analyses

• The data requires multiple analyses.

17. Crisis → Crises

• Economic crises affect everyone.

18. Thesis → Theses

• PhD students defend their theses.

19. Phenomenon → Phenomena

• Natural phenomena like auroras.

20. Criterion → Criteria

• The criteria are strict.

21. Bacterium → Bacteria

• Wash hands to kill bacteria.

22. Curriculum → Curricula (or "curriculums")

• School curricula vary.

23. Memorandum → Memoranda (or "memorandums")

• Sign these memoranda.

24. Datum → Data (now often treated as singular)

• The data shows a trend.

25. Index → Indices (in math/science) or Indexes (in books)

• Stock market indices fell.

26. Matrix → Matrices (math)

• Solve these matrices.

27. Vertex → Vertices (geometry)

• A cube has eight vertices.

28. Appendix → Appendices (books) or Appendixes (medical)

• See the appendices for details.

29. Alumnus → Alumni (male/mixed group)

• Harvard alumni met for reunion.

30. Alumna → Alumnae (female group)

• The alumnae donated funds.

31. Medium → Media (mass communication) or Mediums (spiritualists)

• Social media is powerful.

32. Stadium → Stadia (rare) or Stadiums (common)

• Football stadiums are huge.

33. Fish → Fish (same plural) or Fishes (for different species)

• I caught three fish.

34. Sheep → Sheep (unchanged)

• A flock of sheep.

35. Deer → Deer

• We saw five deer.

36. Series → Series

• Two TV series.

37. Species → Species

• Endangered species.

38. Aircraft → Aircraft

• Three aircraft flew by.

39. Offspring → Offspring

• The lioness protected her offspring.

40. Scissors → Scissors (always plural)

• Where are the scissors?

41. Pants → Pants

• I bought two pairs of pants.

42. Glasses → Glasses (spectacles)

• Her glasses are stylish.

43. Trousers → Trousers

• These trousers fit well.

44. Headquarters → Headquarters

• The company’s headquarters is in NYC.

45. News → News (uncountable)

• The news is shocking.

46. Economics → Economics (field of study)

• Economics is complex.

47. Physics → Physics

• Physics involves experiments.

48. Politics → Politics

• Politics is divisive.

49. Mathematics → Math(s)

• I love mathematics.

50. Cattle → Cattle (no singular form)

• The cattle are grazing.

Key Notes:

✔ Some words (like fish, sheep) don’t change in plural.
✔ Latin/Greek-origin words often use -i, -a, -ae endings.
✔ Words like news, physics are uncountable and always singular.

Master these, and you’ll avoid common mistakes!