He is an expert in chemical analysis.

We are growing vegetables without using chemical fertilizers.

Oxygen, which is one of the chemical elements, is necessary for us to breathe.

He decided to suspend his studies for health reasons.

I am interested in dermatology.

I love the music of Tenjikuraku.

He bought a new schoolbag.

He is an expert in theoretical physics.

He is an expert in electrodynamics.

Demography is a branch of social science that studies the structure, distribution, and changes in human population.