complexity vs complexness

complexity and complexness both are nouns.

Word	Noun	Adjective	Verb	Adverb
complexity	Yes	No	No	No
complexness	Yes	No	No	No

As nouns, complexity and complexness are synonyms defined as:

complexity and complexness: the quality of being intricate and compounded

complexity (noun)	complexness (noun)
the quality of being intricate and compounded	the quality of being intricate and compounded