marumi kumquat vs cumquat

marumi kumquat and cumquat both are nouns.

Word	Noun	Adjective	Verb	Adverb
marumi kumquat	Yes	No	No	No
cumquat	Yes	No	No	No

As nouns, cumquat is a hypernym of marumi kumquat; that is, cumquat is a word with a broader meaning than marumi kumquat:

marumi kumquat: shrub bearing round-fruited kumquats
cumquat: any of several trees or shrubs of the genus Fortunella bearing small orange-colored edible fruits with thick sweet-flavored skin and sour pulp

Other hypernyms of marumi kumquat include kumquat, kumquat tree.

marumi kumquat (noun)	cumquat (noun)
shrub bearing round-fruited kumquats	any of several trees or shrubs of the genus Fortunella bearing small orange-colored edible fruits with thick sweet-flavored skin and sour pulp