Collective nouns refer to groups of people or things, e.g. audience, family, government, team, jury. Collective nouns can usually be treated as singular or plural, with either a singular or plural verb. Both the following sentences are grammatically correct:
The whole family was at the table.
The whole family were at the table.
For more information about this, see matching verbs to collective nouns.
A noun may belong to more than one category. For example, happiness is both a common noun and an abstract noun, while Tower Bridge is both a concrete noun and a proper noun.