He is majoring in psychology.

Gaku is my best friend.

He has a deep interest in archaeology.

My child attends a supplementary school every Saturday.

He has a deep interest in parapsychology.

He understands the meaning of the proverb 'Teaching is half learning', which means that teaching leads to one's own learning.

He is majoring in linguistics.

He has a deep interest in astronomy.

He is an expert in physics.

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