1. Some nouns are always used in the plural. For example:
trousers jeans shorts pyjamas tights scissors glasses/spectacles
You can also use a pair of… with these words:
Example: I need a new pair of jeans or I need some new jeans
2. We do not usually use the plural of person ('persons'). We use people instead.
Example: He is a nice person.
They are nice people.
3. The following nouns end in '-s' but they are not usually plural:
mathematics physics economics athletics gymnastics news
Example: Mathematics is my favorite subject at school
What time is the news on television?
4. The following words end in 's' and can be singular or plural:
means of transport
series
species a means of transport
a television series
a species of bird many means of transport
two television series
200 species of bird
5. Although the following nouns are singular they are often used with a plural verb. This occurs because we think of these things as a number of people ('they'), not as one thing ('it'):
government staff team family audience committee
Examples:
The government (=they) want to reduce taxes.
The staff (=they) aren't happy with their new working conditions.
Scotland (= they, the players) are playing against France in a football match next week.
A singular verb ('the government wants…') is also possible when we want to emphasize the collective character of an action.
Example: The government welcomes the proposal.
6. We always use a plural verb with the police.
Examples: The police have arrested Tom.
Are the police well-paid?
7. We use a singular verb when we talk about a sum of money, a period of time, a distance, etc.
Examples: Five thousand pounds (=it) was stolen in the robbery.
Three years (=it) is a long time to be without a job.

