He is an expert in ethology, and his research is highly regarded worldwide.

He is the type of person who thinks it's a moonlit night if it's bright, so he only has a one-sided perspective.

He thought deeply and said, 'I think, therefore I am.'

He is a perfectionist, so he is very strict about his work.

He played a perfect fifth scale on the piano.

The indefinite article is a basic part of English grammar.

Mr. Shinobu is my best friend.

This area is a no-entry area.

He was criticized for his unjust actions.

This chemical reaction is irreversible.