Collective nouns are words that refer to a group of people. Examples are: jury, commission, army, committee etc.
A collective noun is followed by a singular verb when the group is thought of as a single unit. However, a plural verb is used when the individual members of the group are thought of.
Examples are given below.
The ship’s crew was a mixed group of different nationalities. (Here the reference is to the crew as a whole.)
When the ship arrived in port, the crew were taken into custody on a charge of mutiny.
A committee was appointed to study the question.
The Committee were divided on the question.
Note that in American English, collective nouns are always treated as singular.
Some nouns are plural in form, but singular in meaning. They should be followed by singular verbs.
The news is too good to be true.
The wages of sin is death.
Politics is a dirty game.
The United Nations is our only hope.
‘Gulliver’s Travels’ is an interesting book.
When the subject is a sum of money considered as a whole, the singular verb is used. When the subject is a sum of money and the reference is to the bills or coins considered separately, the plural verb is used.
A thousand dollars is not a small sum.
A thousand dollars were distributed among the prize winners.
Two thousand dollars is his fee for a single appearance in the Supreme Court.
There were twenty silver coins jingling in his pocket.