memorial vs subject matter

memorial and subject matter both are nouns.

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

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

memorial: a written statement of facts submitted in conjunction with a petition to an authority
subject matter: content communicating a message; what something is about

Other hypernyms of memorial include content, message, substance.

memorial (noun)	subject matter (noun)
a structure erected to commemorate persons or events	content communicating a message; what something is about
a recognition of meritorious service
a written statement of facts submitted in conjunction with a petition to an authority