The regular plural of nouns is made by adding an S to the end of the word.

apple  ⇒  apples

kid ⇒ kids

flower ⇒ flowers

bee ⇒ bees

But there are exceptions to this rule. We call these exceptions irregular plurals.

We make the plural of nouns that end in CH, SH, X, or SS by adding ES.

one dress ⇒ two dresses

one fox ⇒ two foxes

one couch ⇒ two couches

We make the plural of some nouns that end in F or FE by changing the F or FE to V and adding ES.

one leaf ⇒ two leaves

one elf ⇒ two elves

We make the plural of nouns that end in Y not following a vowel by changing the Y to I and adding ES.

one cherry  ⇒ two cherries

one fly ⇒ two flies

And of course, there are many words that just don’t follow a rule.

one woman ⇒ two women

one child ⇒ two children

one sheep ⇒ two sheep

one cactus ⇒ two cacti