Can the same collective noun be used for different groups?

Yes, 'United Nations' can be considered as a collective noun. It represents a group of countries working together for global issues like human rights, health, peace, etc. The United Nations is made up of many members, but is treated as one organization, making it a collective noun.

Example:

• The United Nations has declared a new healthcare policy.
• The United Nations is working to stop climate change.

Yes, 'police' is a collective noun. It represents a body of officers acting together. Additionally, unlike many other English collective nouns, 'police' is always used with a plural verb. Simply put, instead of saying 'police is', we say 'police are'.

For example: 

• The police have arrested the thief.
• The police are patroling on the streets of New York.

Collective nouns for animals are the English words used to name a group of the same species. For instance, instead of saying 'many lions' we say 'a pride of lions'. Similarly, there are unique names for different groups of animals. 

Collective Nouns of Animals Examples

• A murder of crows
• A gaggle of geese
• A school of fish
• A flock of birds
• a tower of giraffes
• A drove of horses
• A nest of mice

No, collective nouns are not just restricted to objects. According to Oxford Dictionary collective noun is, “a singular noun, such as committee or team, that refers to a group of people, animals or things. 

Here are some collective nouns examples for reference.

Yes, there are many collective nouns in English that are used for groups of people. For instance, in school we use class for students, and in music, we use choir for singers.

Collective Nouns for People

• A committee of members
• A crowd of spectators
• A herd of harlots
• A gang of prisoners
• A giggle of girls
• A pack of thieves
• A panel of experts
• A mob of rioters