publicity vs subject matter

publicity and subject matter both are nouns.

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

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

publicity: a message issued in behalf of some product or cause or idea or person or institution
subject matter: content communicating a message; what something is about

Other hypernyms of publicity include content, message, substance.

publicity (noun)	subject matter (noun)
the quality of being open to public view	content communicating a message; what something is about
a message issued in behalf of some product or cause or idea or person or institution