scriptwriter vs writer

scriptwriter and writer both are nouns.

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

As nouns, writer is a hypernym of scriptwriter; that is, writer is a word with a broader meaning than scriptwriter:

scriptwriter: someone who writes scripts for plays or movies or broadcast dramas
writer: writes (books or stories or articles or the like) professionally (for pay)

Other hypernyms of scriptwriter include author.

scriptwriter (noun)	writer (noun)
someone who writes scripts for plays or movies or broadcast dramas	writes (books or stories or articles or the like) professionally (for pay)
	a person who is able to write and has written something