chairman vs chair

chairman and chair both are nouns.

Word	Noun	Adjective	Verb	Adverb
chairman	Yes	No	Yes	No
chair	Yes	No	Yes	No

As nouns, chair is a hypernym of chairman; that is, chair is a word with a broader meaning than chairman:

Other hypernyms of chairman include chairperson, president, adult female, woman.

As verbs, chairman and chair are synonyms defined as:

chairman and chair: act or preside as chair, as of an academic department in a university

chairman (noun)	chair (noun)
the male officer who presides at the meetings of an organization	the position of professor
	a seat for one person, with a support for the back
	an instrument of execution by electrocution; resembles an ordinary seat for one person
	a particular seat in an orchestra
	the officer who presides at the meetings of an organization

chairman (verb)	chair (verb)
act or preside as chair, as of an academic department in a university	preside over
	act or preside as chair, as of an academic department in a university