Irregular plurals

Most nouns make their plural with ⟦-s⟧ or ⟦-es⟧, but some don't follow the rules. These irregular plurals change their vowel, add a different ending, change ⟦f⟧ to ⟦v⟧ or stay exactly the same. You learn them by heart, and saying them out loud helps.

Key facts

  • Some nouns change their vowel: ⟦man → men⟧, ⟦woman → women⟧, ⟦foot → feet⟧, ⟦tooth → teeth⟧, ⟦goose → geese⟧, ⟦mouse → mice⟧.
  • A few add ⟦-en⟧ or ⟦-ren⟧: ⟦child → children⟧, ⟦ox → oxen⟧. And ⟦person → people⟧.
  • Some stay the same: ⟦one sheep, two sheep⟧; also ⟦deer⟧, ⟦fish⟧ and ⟦aircraft⟧.
  • Many nouns ending in ⟦f⟧ or ⟦fe⟧ change to ⟦-ves⟧: ⟦knife → knives⟧, ⟦leaf → leaves⟧, ⟦half → halves⟧. But some just add ⟦-s⟧: ⟦roof → roofs⟧, ⟦chef → chefs⟧, ⟦cliff → cliffs⟧.
  • Some words from Latin and Greek keep their own plurals: ⟦cactus → cacti⟧, ⟦crisis → crises⟧, ⟦phenomenon → phenomena⟧, ⟦criterion → criteria⟧.

Worked examples

Example 1

Write the plural: ⟦one child, three ___⟧

  1. ⟦Childs⟧ is not a word: ⟦child⟧ is irregular.
  2. Its plural adds ⟦-ren⟧: ⟦child → children⟧.
  3. ⟦one child, three children⟧

Answer: ⟦children⟧

Example 2

Write the plural of ⟦knife⟧.

  1. ⟦Knife⟧ ends in ⟦fe⟧.
  2. Change ⟦fe⟧ to ⟦v⟧ and add ⟦-es⟧: you can hear the ⟦v⟧ when you say it.
  3. ⟦knife → knives⟧

Answer: ⟦knives⟧

Example 3

Choose: ⟦The farmer has twenty (sheep / sheeps).⟧

  1. ⟦Sheep⟧ is the same in the singular and the plural.
  2. ⟦The farmer has twenty sheep.⟧

Answer: ⟦sheep⟧

Example 4

Correct the mistake: ⟦My foots are wet.⟧

  1. ⟦Foot⟧ makes its plural by changing ⟦oo⟧ to ⟦ee⟧.
  2. ⟦My feet are wet.⟧

Answer: ⟦My feet are wet.⟧