Irregular Plural Nouns Worksheet - ALL ESL - Free Printable

Let’s go through each singular noun and convert it to its irregular plural form. I’ll list them one by one and make sure each is correct.

1. Man → Men
2. Foot → Feet
3. Tooth → Teeth
4. Mouse → Mice
5. Person → People
6. Deer → Deer (same in plural)
7. Child → Children
8. Woman → Women
9. Quiz → Quizzes (this one adds “-es” because it ends in ‘z’ — still irregular compared to regular nouns)
10. Tuna → Tuna (same in plural — often used as both singular and plural)
11. Bacterium → Bacteria
12. Crisis → Crises
13. Series → Series (same in plural)
14. Index → Indices (or indexes — but “indices” is the more traditional irregular form)
15. Fungus → Fungi
16. Cactus → Cacti
17. Axis → Axes
18. Datum → Data
19. Analysis → Analyses
20. Formula → Formulas (or formulae — both are accepted, but “formulas” is more common now; however, since this is an “irregular” worksheet, “formulae” may be expected — we’ll use “formulae” for consistency with Latin plurals)

Wait — let’s double-check #9: “Quiz” → “Quizzes” — yes, that’s correct. Even though it looks like a regular plural, it’s technically irregular because you double the ‘z’ and add ‘es’. Some might argue it’s regular, but in many school worksheets, it’s grouped under irregular due to spelling change.

#10: “Tuna” — usually stays “tuna” in plural (e.g., “two tuna”), so that’s correct.

#13: “Series” — same in singular and plural — correct.

#14: “Index” — “indices” is the classical plural, especially in academic contexts — good choice here.

#20: “Formula” — “formulae” is the Latin plural, which fits the theme of irregular plurals from Latin/Greek — so we’ll go with “formulae”.

All checked. Ready to write final answers.

Final Answer:
1. Men
2. Feet
3. Teeth
4. Mice
5. People
6. Deer
7. Children
8. Women
9. Quizzes
10. Tuna
11. Bacteria
12. Crises
13. Series
14. Indices
15. Fungi
16. Cacti
17. Axes
18. Data
19. Analyses
20. Formulae