assembly plant vs manufactory

assembly plant and manufactory both are nouns.

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

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

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

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

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