He is an expert in bibliography and has many publications.

He is an expert in sociology.

Taxonomy is the science of finding, understanding, and naming species of organisms.

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

He is majoring in mineralogy at university.

He is an expert in entomology, especially knowledgeable about butterflies.

Cytology is a branch of biology that studies the structure and function of cells.

He is majoring in economics.

He is an expert in bacteriology.

He is majoring in zoology at university.