Plurals of nouns: special cases

 In English, there are some special cases when it comes to forming the plural of nouns. Here's an overview of some of the most common special cases:

1. Irregular plurals: Some nouns have irregular plural forms that do not follow the standard "-s" or "-es" rules.

• man -> men
• woman -> women
• child -> children
• tooth -> teeth
• foot -> feet
• goose -> geese
• mouse -> mice
• louse -> lice

2. Nouns ending in "-y": For nouns ending in "-y," the plural form is typically formed by changing "-y" to "-ies" if the noun ends in a consonant + "-y." If the noun ends in a vowel + "-y," add "-s" to form the plural.

• baby -> babies (consonant + -y)
• city -> cities (consonant + -y)
• toy -> toys (vowel + -y)
• boy -> boys (vowel + -y)

3. Nouns ending in "-f" or "-fe": Some nouns ending in "-f" or "-fe" change to "-ves" in the plural.

• leaf -> leaves
• half -> halves
• knife -> knives
• wife -> wives

However, this rule does not apply to all such nouns. Some just add "-s" to form the plural.

• roof -> roofs
• belief -> beliefs
• chef -> chefs

4. Nouns with the same singular and plural forms: Some nouns have the same form in both singular and plural.

• sheep -> sheep
• deer -> deer
• fish -> fish (though "fishes" is also accepted in some contexts)
• aircraft -> aircraft

5. Compound nouns: For compound nouns, usually, the main or first part of the word changes to form the plural.

• toothbrush -> toothbrushes
• passer-by -> passers-by
• mother-in-law -> mothers-in-law

6. Foreign plurals: Some nouns borrowed from other languages retain their original plural forms.

• cactus -> cacti (Latin origin)
• fungus -> fungi (Latin origin)
• datum -> data (Latin origin)
• index -> indices (Latin origin)
• crisis -> crises (Greek origin)
• phenomenon -> phenomena (Greek origin)

7. Collective nouns: Some nouns represent a group or collection of things and can be treated as singular or plural, depending on the context.

• team -> teams (plural)
• family -> families (plural)
• government -> governments (plural)

These special cases might seem confusing at first, but with practice and exposure to different contexts, you will become more adept at forming and recognizing plural nouns.