treadwheel vs treadmill

treadwheel and treadmill both are nouns.

Word	Noun	Adjective	Verb	Adverb
treadwheel	Yes	No	No	No
treadmill	Yes	No	No	No

As nouns, treadwheel and treadmill are synonyms defined as:

treadwheel and treadmill: a mill that is powered by men or animals walking on a circular belt or climbing steps

Other synonyms of treadwheel include tread-wheel.

treadwheel (noun)	treadmill (noun)
a mill that is powered by men or animals walking on a circular belt or climbing steps	a job involving drudgery and confinement
	a mill that is powered by men or animals walking on a circular belt or climbing steps
	an exercise device consisting of an endless belt on which a person can walk or jog without changing place