flatness vs gustatory sensation

flatness and gustatory sensation both are nouns.

Word	Noun	Adjective	Verb	Adverb
flatness	Yes	No	No	No
gustatory sensation	Yes	No	No	No

As nouns, gustatory sensation is a hypernym of flatness; that is, gustatory sensation is a word with a broader meaning than flatness:

flatness: a deficiency in flavor
gustatory sensation: the sensation that results when taste buds in the tongue and throat convey information about the chemical composition of a soluble stimulus

Other hypernyms of flatness include gustatory perception, taste, taste perception, taste sensation.

flatness (noun)	gustatory sensation (noun)
the property of having two dimensions	the sensation that results when taste buds in the tongue and throat convey information about the chemical composition of a soluble stimulus
inactivity; showing an unusual lack of energy
the property of having little or no contrast; lacking highlights or gloss
a deficiency in flavor
a want of animation or brilliance