half-relief vs embossment

half-relief and embossment both are nouns.

Word	Noun	Adjective	Verb	Adverb
half-relief	Yes	No	No	No
embossment	Yes	No	No	No

As nouns, embossment is a hypernym of half-relief; that is, embossment is a word with a broader meaning than half-relief:

half-relief: a sculptural relief between low relief and high relief
embossment: sculpture consisting of shapes carved on a surface so as to stand out from the surrounding background

Other hypernyms of half-relief include relief, relievo, rilievo, sculptural relief.

half-relief (noun)	embossment (noun)
a sculptural relief between low relief and high relief	sculpture consisting of shapes carved on a surface so as to stand out from the surrounding background
	an impression produced by pressure or printing