eye mask vs half mask

eye mask and half mask both are nouns.

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

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

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

Other synonyms of eye mask include domino.

eye mask (noun)	half 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