empirical research vs inquiry

empirical research and inquiry both are nouns.

Word	Noun	Adjective	Verb	Adverb
empirical research	Yes	No	No	No
inquiry	Yes	No	No	No

As nouns, inquiry is a hypernym of empirical research; that is, inquiry is a word with a broader meaning than empirical research:

Other hypernyms of empirical research include enquiry, research.

empirical research (noun)	inquiry (noun)
an empirical search for knowledge	a systematic investigation of a matter of public interest
	a search for knowledge
	an instance of questioning