mask vs gasmask

mask and gasmask both are nouns.

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

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

mask: a protective covering worn over the face
gasmask: a protective mask with a filter; protects the face and lungs against poisonous gases

Other hyponyms of mask include face mask, gas helmet, respirator, welder's mask.

mask (noun)	gasmask (noun)
activity that tries to conceal something	a protective mask with a filter; protects the face and lungs against poisonous gases
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)	gasmask (verb)
put a mask on or cover with a mask
shield from light
cover with a sauce
hide under a false appearance
make unrecognizable