severity vs austereness

severity and austereness both are nouns.

Word	Noun	Adjective	Verb	Adverb
severity	Yes	No	No	No
austereness	Yes	No	No	No

As nouns, severity and austereness are synonyms defined as:

Other synonyms of severity include severeness.

severity (noun)	austereness (noun)
excessive sternness	extreme plainness
used of the degree of something undesirable e.g. pain or weather
something hard to endure
extreme plainness