promotion vs subject matter

promotion and subject matter both are nouns.

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

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

promotion: 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 promotion include content, message, substance.

promotion (noun)	subject matter (noun)
act of raising in rank or position	content communicating a message; what something is about
the advancement of some enterprise
a message issued in behalf of some product or cause or idea or person or institution
encouragement of the progress or growth or acceptance of something