triumphal arch vs monument

triumphal arch and monument both are nouns.

Word	Noun	Adjective	Verb	Adverb
triumphal arch	Yes	No	No	No
monument	Yes	No	No	No

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

triumphal arch: a monumental archway; usually they are built to commemorate some notable victory
monument: a structure erected to commemorate persons or events

Other hypernyms of triumphal arch include arch, memorial.

triumphal arch (noun)	monument (noun)
a monumental archway; usually they are built to commemorate some notable victory	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