Let's gather with friends at the park.

It was decided that friends would gather in the park.

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.

He wants to learn deeply about set theory.

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