He was playing with a cat in the back alley.

He was riding a bicycle on the road.

His main argument was very persuasive.

He met a person on the road.

He was wearing a pendant in the shape of a skull around his neck.

He started cutting trees to make an abatis.

I am learning Russian at university.

He is majoring in logic at university.

Graph theory is a branch of mathematics that studies the structure of networks.

Semiotics is the study of the meaning and use of signs and sign systems.