avower vs postulator

avower and postulator both are nouns.

Word	Noun	Adjective	Verb	Adverb
avower	Yes	No	No	No
postulator	Yes	No	No	No

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

avower: someone who claims to speak the truth
postulator: someone who assumes or takes something for granted as the basis of an argument

avower (noun)	postulator (noun)
someone who admits or acknowledges openly and boldly	someone who assumes or takes something for granted as the basis of an argument
someone who claims to speak the truth	(Roman Catholic Church) someone who proposes or pleads for a candidate for beatification or canonization