rewriting vs rephrasing

rewriting and rephrasing both are nouns.

Word	Noun	Adjective	Verb	Adverb
rewriting	Yes	No	No	No
rephrasing	Yes	No	No	No

As nouns, rephrasing is a hyponym of rewriting; that is, rephrasing is a word with a more specific, narrower meaning than rewriting:

Other hyponyms of rewriting include rescript, revisal, revise, revision, recasting, rewording.

rewriting (noun)	rephrasing (noun)
editing that involves writing something again	changing a particular word or phrase