brownie vs fay

brownie and fay both are nouns.

Word	Noun	Adjective	Verb	Adverb
brownie	Yes	No	No	No
fay	Yes	No	No	No

As nouns, fay is a hypernym of brownie; that is, fay is a word with a broader meaning than brownie:

Other hypernyms of brownie include faerie, faery, fairy, sprite.

brownie (noun)	fay (noun)
square or bar of very rich chocolate cake usually with nuts	a small being, human in form, playful and having magical powers
(folklore) fairies that are somewhat mischievous