practice of medicine vs operate

practice of medicine is a noun but operate is not a noun.

Word	Noun	Adjective	Verb	Adverb
practice of medicine	Yes	No	No	No
operate	No	No	Yes	No

practice of medicine (noun)	operate (noun)
the learned profession that is mastered by graduate training in a medical school and that is devoted to preventing or alleviating or curing diseases and injuries

practice of medicine (verb)	operate (verb)
	perform surgery on
	perform a movement in military or naval tactics in order to secure an advantage in attack or defense
	handle and cause to function
	keep engaged
	perform as expected when applied
	direct or control; projects, businesses, etc.