treadwheel vs milling machinery

treadwheel and milling machinery both are nouns.

Word	Noun	Adjective	Verb	Adverb
treadwheel	Yes	No	No	No
milling machinery	Yes	No	No	No

As nouns, milling machinery is a hypernym of treadwheel; that is, milling machinery is a word with a broader meaning than treadwheel:

treadwheel: a mill that is powered by men or animals walking on a circular belt or climbing steps
milling machinery: machinery that processes materials by grinding or crushing

Other hypernyms of treadwheel include grinder, mill.

treadwheel (noun)	milling machinery (noun)
a mill that is powered by men or animals walking on a circular belt or climbing steps	machinery that processes materials by grinding or crushing