He has a deep interest in etymology.

He is an expert in bryology and is studying many types of moss.

He is good at solving geometry problems.

He is majoring in linguistics.

He is an expert in physics.

Electromagnetism is a part of physics that studies the interaction between electricity and magnetism.

He is an expert in toxicology and conducts many studies.

He has a deep interest in astronomy.

He is an expert in rhetoric, teaching the techniques of speech.

He is globally recognized as an expert in Indology.