brainiac vs genius

brainiac and genius both are nouns.

Word	Noun	Adjective	Verb	Adverb
brainiac	Yes	No	No	No
genius	Yes	No	No	No

As nouns, brainiac and genius are synonyms defined as:

brainiac and genius: someone who has exceptional intellectual ability and originality

Other synonyms of brainiac include brain, Einstein, mastermind.

brainiac (noun)	genius (noun)
someone who has exceptional intellectual ability and originality	exceptional creative ability
	a natural talent
	unusual mental ability
	someone who has exceptional intellectual ability and originality
	someone who is dazzlingly skilled in any field