Category theory is a branch of mathematics that studies structures and their relationships.

He works in the marketing division of the company.

The structure of this building is very complex.

I love mathematics.

He is conducting research on a new energy source.

He is researching about a new energy source.

We have maintained a good relationship for a long time.

His research is deeply related to my project.

This sphere is a part of our life.

This park is a no-smoking area.