The head or leader of any body of men; a commander, as of an army; a head man, as of a tribe, clan, or family; a person in authority who directs the work of others; the principal actor or agent.

The free holder leader of a Town, Tribe, or Abbey. They are referred to as "Milord/lady Chief", and wear a single diadem upon their coronet.

a person who is in charge; "the head of the whole operation"

a leader of a group of people, while a king is the leader of a nation, a whole identifiably unique group of people

In Gaelic taoiseach, the head of a ruling kingroup, pronounced 'tee-shok' (the actual term taoiseach does not appear to have been widely used in Brehon Law tracts, and of course is most familiar today from its use to denote the prime minister of the Republic of Ireland).

in Scotland, the hereditary head of a noble family, usu. descriptive exclusively of the head of a Highland clan and its whole name and arms.