reviewer vs author

reviewer and author both are nouns.

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

As nouns, author is a hypernym of reviewer; that is, author is a word with a broader meaning than reviewer:

reviewer: a writer who reports and analyzes events of the day
author: writes (books or stories or articles or the like) professionally (for pay)

Other hypernyms of reviewer include writer.

reviewer (noun)	author (noun)
a writer who reports and analyzes events of the day	writes (books or stories or articles or the like) professionally (for pay)
someone who reads manuscripts and judges their suitability for publication	someone who originates or causes or initiates something

reviewer (verb)	author (verb)
	be the author of