A collective noun refers to a group of persons, places or things that act as one unit. For example, the collective noun "choir" denotes many people, even though it does not end in "s." The word "choir" refers to one group consisting of many parts, whereas "choirs" refers to many groups consisting of many parts. A verb should always agree with the noun performing its action. How to make a verb agree with a collective noun depends on the meaning behind the sentence.
Singular Collective Noun
When a collective noun denotes a single group of something -- whether persons, places or things -- all acting in unison, it is called a singular collective noun, and its associated verb takes a singular form. Unlike with nouns where an "s" ending signifies plurality, an "s" ending on a verb actually denotes a singular ending. Note that not all verbs, however, take an ending in the plural form. For example, "are" and "have" indicate pluralization.
The singular collective noun "committee" refers to one unit, because it does not end in "s," so it is singular and requires a singular verb conjugation. Therefore, the phrase "The committee approves" is grammatically correct, because both the noun and verb take the singular form. They agree grammatically. Other examples include "The team practices," "The senate votes" and "The crew cleans up."
Plural Collective Noun
In some cases, however, a writer may wish to refer to the individual parts or members of a collective noun. They may be acting separately or against one another, not in unison as one might expect of a group. In this case, the verb would take a plural ending.
If the members of a committee are not acting together, you could write "The committee are working separately." In this sentence, "committee" is a plural collective noun because it refers to the individual members of the group. "The senate are voting tomorrow" means we expect each member to vote differently. "The band have been tuning their instruments" explains that they are tuning them not together, but by themselves.