The concept of the absolute complement plays an important role in set theory.

In math class, I learned about the concept of intersection.

In math class, the teacher explained the concept of relative complement.

Set operation is one of the basic concepts in mathematics.

In math class, we learned about the intersection.

In math class, we learned about the concept of union sets.

He is learning how to use collective nouns.

In mathematics, an empty set refers to a set that does not contain any elements.

A power set is a set consisting of all subsets of a set.

There is a communal letterbox in our apartment.