assembling vs gathering

assembling and gathering both are nouns.

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

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

assembling (noun)	gathering (noun)
the act of gathering something together	the social act of assembling
	the act of gathering something
	sewing consisting of small folds or puckers made by pulling tight a thread in a line of stitching
	a group of persons together in one place