Rules regarding the formation of plurals

In English, we form the plurals of nouns by adding –s to the singular. Examples are given below.

Boy -> boys

Girl -> girls

Book -> books

There are several exceptions to this rule. Nouns ending in –s, -sh, -ch and –x, form their plurals by adding –es to the singular.

Examples are:

Box -> boxes

Class -> classes

Branch -> branches

Brush -> brushes

Watch -> watches

Most nouns ending in –o, generally form their plurals by adding –es.

Examples are:

Mango -> mangoes

Hero -> heroes

Potato -> potatoes

Volcano -> volcanoes

Some singular nouns ending in –o, form their plurals by simply adding –s.

Examples are:

Piano -> pianos

Photo -> photos

Stereo -> stereos

Dynamo -> dynamos

Nouns ending in a consonant + -y, form their plurals by changing that –y into –i and adding –es.

Baby -> babies

Lady -> ladies

City -> cities

Story -> stories

Most nouns ending in –f or –fe form their plurals by changing –f or –fe into v and adding –es.

Leaf -> leaves

Life -> lives

Thief -> thieves

Knife -> knives

There are several exceptions to this rule and the following nouns form their plurals by simply adding –s.

Examples

Roof -> roofs

Proof -> proofs

Dwarf -> dwarfs

Belief -> beliefs

A few nouns form their plurals irregularly. Examples are given below.

Man -> men

Woman -> women

Tooth -> teeth

Mouse -> mice

Some nouns have the singular and the plural alike. Examples are: swine, sheep, deer

The nouns dozen, score, pair, hundred and thousand do not have a plural form when they are used after a number.

The car cost me five thousand dollars. (NOT … five thousands dollars)