treadmill vs tread-wheel

treadmill and tread-wheel both are nouns.

Word	Noun	Adjective	Verb	Adverb
treadmill	Yes	No	No	No
tread-wheel	Yes	No	No	No

As nouns, treadmill and tread-wheel are synonyms defined as:

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

Other synonyms of treadmill include treadwheel.

treadmill (noun)	tread-wheel (noun)
a job involving drudgery and confinement	a mill that is powered by men or animals walking on a circular belt or climbing steps
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