retention vs impermeability

retention and impermeability both are nouns.

Word	Noun	Adjective	Verb	Adverb
retention	Yes	No	No	No
impermeability	Yes	No	No	No

As nouns, impermeability is a hypernym of retention; that is, impermeability is a word with a broader meaning than retention:

retention: the power of retaining liquid
impermeability: the property of something that cannot be pervaded by a liquid

Other hypernyms of retention include impermeableness.

retention (noun)	impermeability (noun)
the act of retaining something	the property of something that cannot be pervaded by a liquid
the power of retaining liquid
the power of retaining and recalling past experience