A collective noun is:

a pride of lions (refers to a group of lions)

a herd of cattle (refers to a group of domestic cattle)

a flock of birds (refers to a group of flying birds)

a set of plans (refers to plans - conceptual)

a set of dinnerware (refers to dinnerware - inanimate object)

a pair of insects (refers to 2 insects)

a trio of chickens (refers to 3 chickens)

a dozen trees (refers to 12 trees)

a score of birds (refers to 20 birds)

a gross of apples (refers to 144 apples)

a ream of paper (refers to 500 sheets of paper)