write up vs newsletter

write up and newsletter both are nouns.

Word	Noun	Adjective	Verb	Adverb
write up	Yes	No	Yes	No
newsletter	Yes	No	No	No

As nouns, newsletter is a hyponym of write up; that is, newsletter is a word with a more specific, narrower meaning than write up:

write up: a short account of the news
newsletter: report or open letter giving informal or confidential news of interest to a special group

Other hyponyms of write up include newssheet, bulletin, communique, despatch, dispatch, urban legend, exclusive, scoop.

write up (noun)	newsletter (noun)
a short account of the news	report or open letter giving informal or confidential news of interest to a special group

write up (verb)	newsletter (verb)
bring to public notice by writing, with praise or condemnation
put into writing; write in complete form