strictness vs hardness

strictness and hardness both are nouns.

Word	Noun	Adjective	Verb	Adverb
strictness	Yes	No	No	No
hardness	Yes	No	No	No

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

strictness (noun)	hardness (noun)
uncompromising resolution	a quality of water that contains dissolved mineral salts that prevent soap from lathering
conscientious attention to rules and details	the property of being rigid and resistant to pressure; not easily scratched; measured on Mohs scale
	the quality of being difficult to do
	devoid of passion or feeling; hardheartedness
	excessive sternness