run down vs sap

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

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

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

Other synonyms of run down include exhaust, play out, tire.

run down (noun)	sap (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

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