flatness vs dimensionality

flatness and dimensionality both are nouns.

Word	Noun	Adjective	Verb	Adverb
flatness	Yes	No	No	No
dimensionality	Yes	No	No	No

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

flatness (noun)	dimensionality (noun)
the property of having two dimensions	the spatial property of having dimensions
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