do work vs exercise

do work is not a noun while exercise is a noun.

Word	Noun	Adjective	Verb	Adverb
do work	No	No	Yes	No
exercise	Yes	No	Yes	No

do work (noun)	exercise (noun)
	the activity of exerting your muscles in various ways to keep fit
	a task performed or problem solved in order to develop skill or understanding
	systematic training by multiple repetitions
	the act of using
	an action, often used negatively and without consequences
	(usually plural) a ceremony that involves processions and speeches

do work (verb)	exercise (verb)
be employed	do physical exercise
	give a workout to
	learn by repetition
	put to use
	carry out or practice; as of jobs and professions