He is known as an expert in pedagogy.

He is an expert in pedagogy and is deeply involved in the educational activities of children.

He is very excellent in the field of arts and sciences.

That theory is unscientific and has no evidence at all.

He is an expert in astrophysics.

He is majoring in belles-lettres.

She is majoring in clinical psychology.

He lost his sense of direction.

Demography is a part of social science that studies the structure, evolution, and problems of human population.

He is studying hard to enter the next level of school.