He needs to worry about his health.

He was demotivated by his failure and decided never to get involved in that business again.

He is showing symptoms of melancholia.

Korumbia is my best friend.

He is a world-renowned bacteriologist.

He is a world-renowned biologist.

He is traveling around the world as an ecologist.

He is a world-famous archaeologist.

He is a beginner in Japanese.

He is a renowned criminologist who has contributed to many crime analyses.