He is majoring in linguistics.

He is good at solving geometry problems.

He is an expert in toxicology and conducts many studies.

He is an expert in bibliography and has many publications.

He is an expert in anatomy.

He is an expert in pathology.

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.