Plural nouns (cats, buses, children)

Most nouns add -s in the plural.

• cat → cats, book → books

-es

After -s, -ss, -sh, -ch, -x, -z: bus → buses, box → boxes, watch → watches.

After -o some nouns take -es (potato → potatoes, tomato → tomatoes, hero → heroes), but many take only -s: photo → photos, piano → pianos, radio → radios. There is no single “all -o → -es” rule.

-y

• consonant + y: city → cities, baby → babies
• vowel + y: boy → boys, day → days

Irregular

• man → men, woman → women, child → children
• foot → feet, tooth → teeth, mouse → mice
• person → people
• No change: sheep → sheep, often fish → fish