exercise vs do work

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

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

exercise (noun)	do work (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

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