He is an expert in geophysics.

He is a world-renowned zoologist.

It's difficult to understand the principles of electrooptics.

Music therapy is very effective in reducing stress.

Astrobiology is a very interesting field of study.

Abstract algebra is a branch of mathematics that studies algebraic structures.

Abstract algebra is a field of mathematics that studies algebraic structures in an abstract way.

I am majoring in econometrics at university.

He is an expert in biophysics.

I am majoring in biophysics at university.