mask vs false face

mask and false face both are nouns.

Word	Noun	Adjective	Verb	Adverb
mask	Yes	No	Yes	No
false face	Yes	No	No	No

As nouns, false face is a hyponym of mask; that is, false face is a word with a more specific, narrower meaning than mask:

Other hyponyms of mask include domino, eye mask, half mask.

mask (noun)	false face (noun)
activity that tries to conceal something	a mask worn as part of a masquerade costume
a covering to disguise or conceal the face
a protective covering worn over the face
a party of guests wearing costumes and masks

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