onion dome vs dome

onion dome and dome both are nouns.

Word	Noun	Adjective	Verb	Adverb
onion dome	Yes	No	No	No
dome	Yes	No	No	No

As nouns, dome is a hypernym of onion dome; that is, dome is a word with a broader meaning than onion dome:

onion dome: a dome that is shaped like a bulb; characteristic of Russian and Byzantine church architecture
dome: a hemispherical roof

onion dome (noun)	dome (noun)
a dome that is shaped like a bulb; characteristic of Russian and Byzantine church architecture	a hemispherical roof
	a stadium that has a roof
	informal terms for a human head
	a concave shape whose distinguishing characteristic is that the concavity faces downward