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.

In math class, we learned about the intersection.

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

There is a communal letterbox in our apartment.

She has trypophobia, and feels discomfort when she sees things with many holes like beehives or corals.

What is the difference between these two products?

He showed understanding towards my explanation.

Please tell me the difference between these two items.

Please tell me the difference between these products.