He is a world-renowned osteologist.

He is a famous osteologist, studying many fossils.

He understands the importance of learning.

He is majoring in psychology.

Gaku is my best friend.

He is a famous psychologist, influencing many people.

My major is chemical engineering.

He is an excellent doctor.

He is a famous author, and his works are loved by many readers.

He lost his job, but he believes in the saying 'when one door shuts, another opens' and is looking for new opportunities.