headman vs leader

headman and leader both are nouns.

Word	Noun	Adjective	Verb	Adverb
headman	Yes	No	No	No
leader	Yes	No	No	No

As nouns, leader is a hypernym of headman; that is, leader is a word with a broader meaning than headman:

headman (noun)	leader (noun)
the head of a tribe or clan	a featured article of merchandise sold at a loss in order to draw customers
an executioner who beheads the condemned person	a person who rules or guides or inspires others