memorial tablet vs monument

memorial tablet and monument both are nouns.

Word	Noun	Adjective	Verb	Adverb
memorial tablet	Yes	No	No	No
monument	Yes	No	No	No

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

Other hypernyms of memorial tablet include memorial.

memorial tablet (noun)	monument (noun)
a memorial made of brass	a structure erected to commemorate persons or events
	a burial vault (usually for some famous person)
	an important site that is marked and preserved as public property