Nouns ending in -f or -fe:
* Knife - Knives
* Wife - Wives
* Life - Lives
* Thief - Thieves
* Wolf - Wolves
Exceptions:
* Roof - Roofs
* Chief - Chiefs
* Proof - Proofs
* Safe - Safes
Nouns ending in -y:
* Baby - Babies
* City - Cities
* Story - Stories
* Berry - Berries
Exceptions:
* Money - Money
* Valley - Valleys
* Key - Keys
Other irregular plurals:
* Child - Children
* Foot - Feet
* Tooth - Teeth
* Goose - Geese
* Man - Men
* Woman - Women
* Person - People
* Ox - Oxen
* Mouse - Mice
* Sheep - Sheep
* Fish - Fish (can also be fishes if referring to different types)
* Series - Series
Note: Some nouns, like "deer," "series," and "fish," have the same singular and plural forms.