He is majoring in mineralogy at university.

I am majoring in machine learning.

I plan to enter a private university next year.

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.