Singular - Deer, Plural - Deer

Singular - Fish, Plural - Fish

Singular - Child, Plural - Children

Singular - Cactus, Plural - Cacti

Singular - Tooth, Plural - Teeth

Singular - Foot, Plural - Feet

Singular - Woman, Plural - Women

Singular - Knife, Plural - Knives

Singular - Crisis, Plural - Crises

Singular - Phenomenon, Plural - Phenomena