Plural of nouns

1) Most nouns in English are regular. To make them plural we add -s to the end:
singular plural
1 book 2 books
1 car 4 cars
1 house 8 houses

2) Some nouns have two very different words for the singular and the plural:
singular plural
1 tooth 2 teeth
1 goose 2 geese
1 foot 2 feet
1 child 2 children
1 ox 2 oxen
1 oasis 2 oases
1 axis 2 axes
1 man 2 men
1 woman 2 women
1 mouse 2 mice
1 medium 2 media
3) Some nouns are the same whether they are singular or plural:
singular plural
1 sheep 2 sheep
1 salmon 2 salmon
1 aircraft 2 aircraft
1 trout 2 trout

4) Some nouns have alternative plurals:
singular plural
1 penny 2 pence/pennies
1 person 2 persons/people
1 fish 2 fish/fishes

no singular; singular plurals; singular & plural; collective; measurement; pair nouns

1) Some nouns have a plural but no singular, for example:
clothes, contents, earnings, goods, riches, savings, thanks, troops

These nouns take a plural verb:
The contents are labelled on the jar.
His savings were wiped out in the crash.

2) Some nouns look plural but are, in fact, singular, for example:
athletics, gymnastics, mathematics, measles, news, politics

The verb is singular here:

His measles is spreading.
Politics is boring!

3) Some words are either plural or singular, for example:
headquarters, means, works (= factory/workshop, etc.)

The verb can be either singular or plural; there is no real difference:

Their headquarters are situated in central London.
Their headquarters is situated in central London.

4) A collective noun describes a group of nouns describing the same thing, for example:
army, Arsenal, audience, class, club, committee, company, crowd, gang, group, Microsoft, public, team, the BBC

We use singular verb if we think of the group as a whole:
Arsenal is playing well today.
Or plural if we are thinking of the individuals:
Arsenal are a mixed bunch of players.
Some groups, however, are always plural:
The police are coming!
The cattle are lowing.

5) When we have a noun phrase of measurement, we use a singular verb:

Twenty kilos is the maximum weight for suitcases.

Six feet six inches is tall for a man.

6) When we talk about a pair of things, we always use the plural, for example:
a pair of: glasses, jeans, scissors, trousers

We use a plural verb:

Your jeans are ripped.