He has expert knowledge.

He is studying computer science at a specialized school.

He is a specialist fool, with no interest in anything outside his field.

He couldn't say anything about issues outside of his field of expertise.

There are many different specialty stores in this town.

He is an expert in medicine.

He is learning the basics of elementary learning.

He clenched his lower jaw tightly to endure the pain.

Gagaku is the ancient court ritual music of Japan.

Ecology is a field of study that investigates the interrelationships of organisms in the natural world.