plaque vs memorial

plaque and memorial both are nouns.

Word	Noun	Adjective	Verb	Adverb
plaque	Yes	No	No	No
memorial	Yes	No	No	No

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

Other hypernyms of plaque include monument.

plaque (noun)	memorial (noun)
a memorial made of brass	a structure erected to commemorate persons or events
(pathology) a small abnormal patch on or inside the body	a recognition of meritorious service
	a written statement of facts submitted in conjunction with a petition to an authority