He is majoring in zoology at university.

He is majoring in geology.

He has a deep interest in teratology.

He is an expert in geography.

He is known as an expert in oncology.

Genetics is a branch of biology that studies the function of genes and the laws of inheritance.

He is an expert in seismology.

Phonetics is a part of linguistics that studies the physical, physiological, and psychological aspects of sounds.

He is majoring in economics.

He is an expert in immunology.