speechwriter vs author

speechwriter and author both are nouns.

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

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

speechwriter: a writer who composes speeches for others to deliver
author: writes (books or stories or articles or the like) professionally (for pay)

Other hypernyms of speechwriter include writer.

speechwriter (noun)	author (noun)
a writer who composes speeches for others to deliver	writes (books or stories or articles or the like) professionally (for pay)
	someone who originates or causes or initiates something

speechwriter (verb)	author (verb)
	be the author of