I. -ory 1 / ə ri $ ɔːri, ə ri/ BrE AmE suffix [in nouns]
a place or thing that is used for doing something:
an observatory (=a place from where people watch something, especially the stars)
II. -ory 2 BrE AmE suffix [in adjectives]
describes something that does a particular thing:
an explanatory note (=that gives an explanation)
a congratulatory telegram (=that congratulates someone)