assembly plant vs factory

assembly plant and factory both are nouns.

Word	Noun	Adjective	Verb	Adverb
assembly plant	Yes	No	No	No
factory	Yes	No	No	No

As nouns, factory is a hypernym of assembly plant; that is, factory is a word with a broader meaning than assembly plant:

assembly plant: a factory where manufactured parts are assembled into a finished product
factory: a plant consisting of one or more buildings with facilities for manufacturing

Other hypernyms of assembly plant include manufactory, manufacturing plant, mill.

assembly plant (noun)	factory (noun)
a factory where manufactured parts are assembled into a finished product	a plant consisting of one or more buildings with facilities for manufacturing