severeness vs harshness

severeness and harshness both are nouns.

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

As nouns, severeness and harshness are synonyms defined as:

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

severeness (noun)	harshness (noun)
extreme plainness	the quality of being harsh or rough or grating to the senses
excessive sternness	excessive sternness
something hard to endure	the roughness of a substance that causes abrasions
used of the degree of something undesirable e.g. pain or weather	the quality of being cruel and causing tension or annoyance