fruitless vs vain

fruitless and vain both are adjectives.

Word	Noun	Adjective	Verb	Adverb
fruitless	No	Yes	No	No
vain	No	Yes	No	No

As adjectives, fruitless and vain are synonyms defined as:

Other synonyms of fruitless include bootless, futile, sleeveless.

fruitless (adjective)	vain (adjective)
unproductive of success	characteristic of false pride; having an exaggerated sense of self-importance
	unproductive of success