mask vs hiding

mask and hiding both are nouns.

Word	Noun	Adjective	Verb	Adverb
mask	Yes	No	Yes	No
hiding	Yes	No	No	No

As nouns, hiding is a hypernym of mask; that is, hiding is a word with a broader meaning than mask:

Other hypernyms of mask include concealing, concealment.

mask (noun)	hiding (noun)
activity that tries to conceal something	the activity of keeping something secret
a covering to disguise or conceal the face	the state of being hidden
a protective covering worn over the face
a party of guests wearing costumes and masks

mask (verb)	hiding (verb)
put a mask on or cover with a mask
shield from light
cover with a sauce
hide under a false appearance
make unrecognizable