author vs authorial

author is a noun but authorial is not a noun.

Word	Noun	Adjective	Verb	Adverb
author	Yes	No	Yes	No
authorial	No	Yes	No	No

author (noun)	authorial (noun)
writes (books or stories or articles or the like) professionally (for pay)
someone who originates or causes or initiates something

author (adjective)	authorial (adjective)
	of or by or typical of an author

author (verb)	authorial (verb)
be the author of