signification vs subject matter

signification and subject matter both are nouns.

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

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

Other hypernyms of signification include content, message, substance.

signification (noun)	subject matter (noun)
the message that is intended or expressed or signified	content communicating a message; what something is about