He commutes to school by bicycle every day.

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.