postulation vs subject matter

postulation and subject matter both are nouns.

Word	Noun	Adjective	Verb	Adverb
postulation	Yes	No	No	No
subject matter	Yes	No	No	No

As nouns, subject matter is a hypernym of postulation; that is, subject matter is a word with a broader meaning than postulation:

postulation: a formal message requesting something that is submitted to an authority
subject matter: content communicating a message; what something is about

Other hypernyms of postulation include content, message, substance.

postulation (noun)	subject matter (noun)
(logic) a declaration of something self-evident; something that can be assumed as the basis for argument	content communicating a message; what something is about
a formal message requesting something that is submitted to an authority