gathering vs convention

gathering and convention both are nouns.

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

As nouns, convention is a hyponym of gathering; that is, convention is a word with a more specific, narrower meaning than gathering:

gathering (noun)	convention (noun)
the social act of assembling	the act of convening
the act of gathering something	orthodoxy as a consequence of being conventional
sewing consisting of small folds or puckers made by pulling tight a thread in a line of stitching	something regarded as a normative example
a group of persons together in one place	(diplomacy) an international agreement
	a large formal assembly