chair vs chairman

chair and chairman both are nouns.

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

As nouns, chairman is a hyponym of chair; that is, chairman is a word with a more specific, narrower meaning than chair:

Other hyponyms of chair include Kalon Tripa, vice chairman, chairwoman.

As verbs, chair and chairman are synonyms defined as:

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

chair (noun)	chairman (noun)
the position of professor	the male officer who presides at the meetings of an organization
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

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