imperviousness vs impenetrability

imperviousness and impenetrability both are nouns.

Word	Noun	Adjective	Verb	Adverb
imperviousness	Yes	No	No	No
impenetrability	Yes	No	No	No

As nouns, imperviousness and impenetrability are synonyms defined as:

imperviousness and impenetrability: the quality of being impenetrable (by people or light or missiles etc.)

imperviousness (noun)	impenetrability (noun)
the quality of being impenetrable (by people or light or missiles etc.)	the quality of being impenetrable (by people or light or missiles etc.)
	incomprehensibility by virtue of being too dense to understand