sap vs run down

sap is a noun but run down is not a noun.

Word	Noun	Adjective	Verb	Adverb
sap	Yes	No	Yes	No
run down	No	No	Yes	No

As verbs, sap and run down are synonyms defined as:

Other synonyms of sap include exhaust, play out, tire.

sap (noun)	run down (noun)
a piece of metal covered by leather with a flexible handle; used for hitting people
a person who lacks good judgment
a watery solution of sugars, salts, and minerals that circulates through the vascular system of a plant

sap (verb)	run down (verb)
excavate the earth beneath	use up all one's strength and energy and stop working
deplete	injure or kill by knocking (someone or something) down and passing over the body, as with a vehicle
	pursue until captured
	move downward
	examine hastily
	deplete
	trace