firmness vs sureness

firmness and sureness both are nouns.

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

As nouns, sureness is a hyponym of firmness; that is, sureness is a word with a more specific, narrower meaning than firmness:

firmness: the quality of being steady or securely and immovably fixed in place
sureness: the quality of being steady and unfailing

Other hyponyms of firmness include granite, stability, stableness.

firmness (noun)	sureness (noun)
the quality of being steady or securely and immovably fixed in place	the quality of being steady and unfailing
the trait of being resolute	freedom from doubt; belief in yourself and your abilities
the property of being unyielding to the touch
the muscle tone of healthy tissue