Thinker (noun)

A person who is able to think deeply and critically about a subject or problem.

Origin:

Late 16th century: from think + -er.

Examples:

1. Einstein was a great thinker and his theories changed our understanding of the universe.
2. The thinker was lost in thought, trying to solve the puzzle.
3. The philosopher was considered one of the greatest thinkers of all time.
4. The young girl was a gifted thinker and showed great promise for the future.
5. The writer was known as a deep thinker and his works often explored complex ideas.