impregnability vs invulnerability

impregnability and invulnerability both are nouns.

Word	Noun	Adjective	Verb	Adverb
impregnability	Yes	No	No	No
invulnerability	Yes	No	No	No

As nouns, impregnability and invulnerability are synonyms defined as:

impregnability and invulnerability: having the strength to withstand attack

impregnability (noun)	invulnerability (noun)
having the strength to withstand attack	the property of being invulnerable; the property of being incapable of being hurt (physically or emotionally)
	having the strength to withstand attack