Nouns - Introduction
Rules regarding Number - Singular or Plural
A collective noun takes a singular verb when the whole group is considered as one unit.
When a material noun denotes a mass of matter, it is not used in the plural form.
There are nouns that have the same form for the plural as well as for singular. Some of them are:
aircraft, deer, offspring, salmon, sheep, space, species, yoke
Some nouns are used in the singular only always.
Some of them are:
advice,clothing, corn, grain, hair, information, justice, poetry, scenery
Some nouns are used in plural form only always.
Some of them are:
biceps, bowels, doldrums, earnings, gallows, genitals, scissors, trousers