gremlin vs fay

gremlin and fay both are nouns.

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

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

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

gremlin (noun)	fay (noun)
(folklore) fairies that are somewhat mischievous	a small being, human in form, playful and having magical powers