irrationality vs unreason

irrationality and unreason both are nouns.

Word	Noun	Adjective	Verb	Adverb
irrationality	Yes	No	No	No
unreason	Yes	No	No	No

As nouns, irrationality and unreason are synonyms defined as:

irrationality and unreason: the state of being irrational; lacking powers of understanding

irrationality (noun)	unreason (noun)
the state of being irrational; lacking powers of understanding	the state of being irrational; lacking powers of understanding