author vs writer

author and writer both are nouns.

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

As nouns, author and writer are synonyms defined as:

author and writer: writes (books or stories or articles or the like) professionally (for pay)

author (noun)	writer (noun)
writes (books or stories or articles or the like) professionally (for pay)	writes (books or stories or articles or the like) professionally (for pay)
someone who originates or causes or initiates something	a person who is able to write and has written something

author (verb)	writer (verb)
be the author of