empirical research vs enquiry

empirical research and enquiry both are nouns.

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

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

Other hypernyms of empirical research include inquiry, research.

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