megalith vs memorial

megalith and memorial both are nouns.

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

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

megalith: memorial consisting of a very large stone forming part of a prehistoric structure (especially in western Europe)
memorial: a structure erected to commemorate persons or events

Other hypernyms of megalith include monument.

megalith (noun)	memorial (noun)
memorial consisting of a very large stone forming part of a prehistoric structure (especially in western Europe)	a structure erected to commemorate persons or events
	a recognition of meritorious service
	a written statement of facts submitted in conjunction with a petition to an authority