half mask vs eye mask

half mask and eye mask both are nouns.

Word	Noun	Adjective	Verb	Adverb
half mask	Yes	No	No	No
eye mask	Yes	No	No	No

As nouns, half mask and eye mask are synonyms defined as:

half mask and eye mask: a mask covering the upper part of the face but with holes for the eyes

Other synonyms of half mask include domino.

half mask (noun)	eye mask (noun)
a mask covering the upper part of the face but with holes for the eyes	a mask covering the upper part of the face but with holes for the eyes