chief

noun

1. the head or leader of a group, organization, etc.; person of highest title or authority
2. Archaic the most valuable or main part of anything
3. Heraldry the upper third of a shield
4. Naut. a chief engineer or chief petty officer

adjective

1. highest, as in rank or office; foremost: the chief magistrate
2. most important or significant; main; principal: the chief advantages

adverb