treadwheel vs tread-wheel

treadwheel and tread-wheel both are nouns.

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

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

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

Other synonyms of treadwheel include treadmill.

treadwheel (noun)	tread-wheel (noun)
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