production line vs mill

production line and mill both are nouns.

Word	Noun	Adjective	Verb	Adverb
production line	Yes	No	No	No
mill	Yes	No	Yes	No

production line (noun)	mill (noun)
mechanical system in a factory whereby an article is conveyed through sites at which successive operations are performed on it	the act of grinding to a powder or dust
	machinery that processes materials by grinding or crushing
	a plant consisting of one or more buildings with facilities for manufacturing

production line (verb)	mill (verb)
	grind with a mill
	produce a ridge around the edge of
	roll out (metal) with a rolling machine
	move about in a confused manner