prolong vs sustain

prolong and sustain both are verbs.

Word	Noun	Adjective	Verb	Adverb
prolong	No	No	Yes	No
sustain	No	No	Yes	No

As verbs, prolong and sustain are synonyms defined as:

Other synonyms of prolong include keep up.

prolong (verb)	sustain (verb)
lengthen in time; cause to be or last longer	undergo (as of injuries and illnesses)
lengthen or extend in duration or space	establish or strengthen as with new evidence or facts
	admit as valid
	supply with necessities and support
	provide with nourishment
	be the physical support of; carry the weight of
	lengthen or extend in duration or space