black Maria vs van

black Maria and van both are nouns.

Word	Noun	Adjective	Verb	Adverb
black Maria	Yes	No	No	No
van	Yes	No	No	No

As nouns, van is a hypernym of black Maria; that is, van is a word with a broader meaning than black Maria:

black Maria (noun)	van (noun)
van used by police to transport prisoners	a truck with an enclosed cargo space
	a camper equipped with living quarters
	(Great Britain) a closed railroad car that carries baggage or freight
	the leading units moving at the head of an army
	any creative group active in the innovation and application of new concepts and techniques in a given field (especially in the arts)