severeness vs hardness

severeness and hardness both are nouns.

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

As nouns, severeness and hardness are synonyms defined as:

Other synonyms of severeness include harshness, inclemency, rigor, rigorousness, rigour, rigourousness, severity, stiffness.

severeness (noun)	hardness (noun)
extreme plainness	a quality of water that contains dissolved mineral salts that prevent soap from lathering
excessive sternness	the property of being rigid and resistant to pressure; not easily scratched; measured on Mohs scale
something hard to endure	the quality of being difficult to do
used of the degree of something undesirable e.g. pain or weather	devoid of passion or feeling; hardheartedness
	excessive sternness