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.

Do you know this secular speech?

Vulgar Latin was the common language of ancient Rome.

Following the customs of the time, they celebrated the festival.

It is important to respect and understand Japanese customs.

The customs of this region are very interesting from a historical perspective.