sarcastic vs irony

sarcastic is not a noun while irony is a noun.

Word	Noun	Adjective	Verb	Adverb
sarcastic	No	Yes	No	No
irony	Yes	No	No	No

sarcastic (noun)	irony (noun)
	incongruity between what might be expected and what actually occurs
	a trope that involves incongruity between what is expected and what occurs
	witty language used to convey insults or scorn

sarcastic (adjective)	irony (adjective)
expressing or expressive of ridicule that wounds