exogamy vs exogamous

exogamy is a noun but exogamous is not a noun.

Word	Noun	Adjective	Verb	Adverb
exogamy	Yes	No	No	No
exogamous	No	Yes	No	No

exogamy (noun)	exogamous (noun)
marriage to a person belonging to a tribe or group other than your own as required by custom or law

exogamy (adjective)	exogamous (adjective)
	pertaining to or characterized by the custom of marrying only outside the limits of a clan or tribe
	characterized by or fit for fertilization by a flower that is not closely related