That theory is unscientific and has no evidence at all.

He is an expert in astrophysics.

He is majoring in belles-lettres.

He lost his sense of direction.

My younger brother will enter the faculty of law next year.

He commutes to school by bicycle every day.

He decided to drop out of school due to the difficulty of his studies.

He is a world-famous mathematician.

He is an expert in ornithology, studying types of birds all over the world.

He has a deep interest in etymology.