hardship vs severeness

hardship and severeness both are nouns.

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

As nouns, hardship and severeness are synonyms defined as:

Other synonyms of hardship include asperity, grimness, rigor, rigorousness, rigour, rigourousness, severity.

hardship (noun)	severeness (noun)
something hard to endure	extreme plainness
something that causes or entails suffering	excessive sternness
a state of misfortune or affliction	something hard to endure
	used of the degree of something undesirable e.g. pain or weather