subpoena vs writ

subpoena and writ both are nouns.

Word	Noun	Adjective	Verb	Adverb
subpoena	Yes	No	Yes	No
writ	Yes	No	No	No

As nouns, writ is a hypernym of subpoena; that is, writ is a word with a broader meaning than subpoena:

subpoena: a writ issued by court authority to compel the attendance of a witness at a judicial proceeding; disobedience may be punishable as a contempt of court
writ: (law) a legal document issued by a court or judicial officer

Other hypernyms of subpoena include judicial writ.

subpoena (noun)	writ (noun)
a writ issued by court authority to compel the attendance of a witness at a judicial proceeding; disobedience may be punishable as a contempt of court	(law) a legal document issued by a court or judicial officer

subpoena (verb)	writ (verb)
serve or summon with a subpoena