sustain vs show

sustain is not a noun while show is a noun.

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

As verbs, show is a hyponym of sustain; that is, show is a word with a more specific, narrower meaning than sustain:

sustain: establish or strengthen as with new evidence or facts
show: establish the validity of something, as by an example, explanation or experiment

Other hyponyms of sustain include back, back up, vouch, verify, demonstrate, establish, prove, shew, document, validate.

sustain (noun)	show (noun)
	an act or social event involving a public performance or entertainment
	pretending that something is the case in order to make a good impression
	something intended to communicate a particular impression

sustain (verb)	show (verb)
undergo (as of injuries and illnesses)	establish the validity of something, as by an example, explanation or experiment
establish or strengthen as with new evidence or facts	provide evidence for
admit as valid	indicate a place, direction, person, or thing; either spatially or figuratively
supply with necessities and support	give expression to
provide with nourishment	give evidence of, as of records
be the physical support of; carry the weight of	indicate a certain reading; of gauges and instruments
lengthen or extend in duration or space	finish third or better in a horse or dog race
	show in, or as in, a picture
	take (someone) to their seats, as in theaters or auditoriums
	make visible or noticeable
	be or become visible or noticeable
	give an exhibition of to an interested audience