convention vs treaty

convention and treaty both are nouns.

Word	Noun	Adjective	Verb	Adverb
convention	Yes	No	No	No
treaty	Yes	No	No	No

As nouns, treaty is a hypernym of convention; that is, treaty is a word with a broader meaning than convention:

Other hypernyms of convention include accord, pact.

convention (noun)	treaty (noun)
the act of convening	a written agreement between two states or sovereigns
orthodoxy as a consequence of being conventional
something regarded as a normative example
(diplomacy) an international agreement
a large formal assembly