interrogatory vs interrogation

interrogatory and interrogation both are nouns.

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

As nouns, interrogatory and interrogation are synonyms defined as:

Other synonyms of interrogatory include examination.

interrogatory (noun)	interrogation (noun)
formal systematic questioning	formal systematic questioning
	a sentence of inquiry that asks for a reply
	an instance of questioning
	a transmission that will trigger an answering transmission from a transponder

interrogatory (adjective)	interrogation (adjective)
relating to the use of or having the nature of an interrogation