Some nouns can be considered either singular or plural, depending on whether the speaker is referring to them as a one group or individually.
Examples of collective nouns are:
The committee has not made a decision yet.
The committee have not made a decision yet.
The team is posing for a photograph.
The team are signing autographs.
(It will submit one conclusion as a group.)
They are still arguing among themselves.)
(as a group)
Be careful when using collective nouns with pronouns.
- The Jones family is having a reunion this Sunday. It meets every summer.
- The Jones family are going home on Monday. They all live in different states.