interrogative vs interrogatory

interrogative and interrogatory both are nouns.

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

As adjectives, interrogative and interrogatory are synonyms defined as:

interrogative and interrogatory: relating to the use of or having the nature of an interrogation

interrogative (noun)	interrogatory (noun)
a sentence of inquiry that asks for a reply	formal systematic questioning
some linguists consider interrogative sentences to constitute a mood

interrogative (adjective)	interrogatory (adjective)
relating to the use of or having the nature of an interrogation	relating to the use of or having the nature of an interrogation
relating to verbs in the so-called interrogative mood