They (referring to women or girls) are my best friends.

He loves indoor sports, especially he often plays basketball.

He is good at playing sonata da camera.

He loves indoor games, especially he is good at Go.

He is playing basketball in the indoor court.

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

There are many different specialty stores in this town.

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

He has expert knowledge.

He is studying computer science at a specialized school.