stability vs firmness

stability and firmness both are nouns.

Word	Noun	Adjective	Verb	Adverb
stability	Yes	No	No	No
firmness	Yes	No	No	No

As nouns, firmness is a hypernym of stability; that is, firmness is a word with a broader meaning than stability:

stability: the quality or attribute of being firm and steadfast
firmness: the quality of being steady or securely and immovably fixed in place

Other hypernyms of stability include steadiness.

stability (noun)	firmness (noun)
the quality or attribute of being firm and steadfast	the quality of being steady or securely and immovably fixed in place
the quality of being enduring and free from change or variation	the trait of being resolute
a stable order (especially of society)	the property of being unyielding to the touch
	the muscle tone of healthy tissue