chair vs presiding officer

chair and presiding officer both are nouns.

Word	Noun	Adjective	Verb	Adverb
chair	Yes	No	Yes	No
presiding officer	Yes	No	No	No

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

chair (noun)	presiding officer (noun)
the position of professor	the leader of a group meeting
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)	presiding officer (verb)
preside over
act or preside as chair, as of an academic department in a university