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

My younger brother will enter the engineering department next year.

He is a world-famous mathematician.

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

He is an expert in psychiatry.

He has a deep interest in etymology.

He is an expert in theoretical physics.

He is an expert in electrodynamics.

Demography is a branch of social science that studies the structure, distribution, and changes in human population.

He has a deep interest in etymology.