MASTER

noun

1. Someone who has control over something or someone.
2. The owner of an animal or slave.
3. The captain of a merchant ship; a master mariner.

verb

1. To be a master.
2. To become the master of; to subject to one's will, control, or authority; to conquer; to overpower; to subdue.
3. To learn to a high degree of proficiency.

adjective

1. Masterful.
2. Main, principal or predominant.
3. Highly skilled.