This form of the word arbitrary is a common misconception. We would normally think that in order to change the word from its adjective form of arbitrary to a noun form of arbitrarity than we would add the ity. In all reality though the correct suffix would be of -ness making the noun form arbitraryness , which would mean: no discernible similarity of signal and meaning.

Hopefully this helps.
Doesn’t the English language cause one to stop and say HU?

Rev. Alimae

Rev. Alimae