mask vs masked ball

mask and masked ball both are nouns.

Word	Noun	Adjective	Verb	Adverb
mask	Yes	No	Yes	No
masked ball	Yes	No	No	No

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

Other hyponyms of mask include fancy-dress ball, masquerade ball.

mask (noun)	masked ball (noun)
activity that tries to conceal something	a ball at which guests wear costumes and masks
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)	masked ball (verb)
put a mask on or cover with a mask
shield from light
cover with a sauce
hide under a false appearance
make unrecognizable