diaglyph vs glyptic art

diaglyph and glyptic art both are nouns.

Word	Noun	Adjective	Verb	Adverb
diaglyph	Yes	No	No	No
glyptic art	Yes	No	No	No

As nouns, glyptic art is a hypernym of diaglyph; that is, glyptic art is a word with a broader meaning than diaglyph:

diaglyph: glyptic art consisting of a sunken or depressed engraving or carving on a stone or gem (as opposed to cameo)
glyptic art: carvings or engravings (especially on precious stones)

Other hypernyms of diaglyph include glyptography.

diaglyph (noun)	glyptic art (noun)
glyptic art consisting of a sunken or depressed engraving or carving on a stone or gem (as opposed to cameo)	carvings or engravings (especially on precious stones)