author vs Koestler

author and Koestler both are nouns.

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

author (noun)	Koestler (noun)
writes (books or stories or articles or the like) professionally (for pay)	British writer (born in Hungary) who wrote a novel exposing the Stalinist purges during the 1930s (1905-1983)
someone who originates or causes or initiates something

author (verb)	Koestler (verb)
be the author of