inquiry vs interrogation

inquiry and interrogation both are nouns.

Word	Noun	Adjective	Verb	Adverb
inquiry	Yes	No	No	No
interrogation	Yes	No	No	No

As nouns, inquiry and interrogation are synonyms defined as:

Other synonyms of inquiry include enquiry, query, question.

inquiry (noun)	interrogation (noun)
a systematic investigation of a matter of public interest	formal systematic questioning
a search for knowledge	a sentence of inquiry that asks for a reply
an instance of questioning	an instance of questioning
	a transmission that will trigger an answering transmission from a transponder