Meaning : A person who is in charge.

Example : The head of the whole operation.

Synonyms : head, top dog

Meaning : A person who exercises control over workers.

Example : If you want to leave early you have to ask the foreman.

Synonyms : boss, foreman, gaffer, honcho

Meaning : The head of a tribe or clan.

Synonyms : chieftain, headman, tribal chief

Meaning : Most important element.

Example : The chief aim of living.
The main doors were of solid glass.
The principal rivers of America.
The principal example.
Policemen were primary targets.
The master bedroom.
A master switch.

Synonyms : main, master, primary, principal