obligatory vs mandatory

obligatory is not a noun while mandatory is a noun.

Word	Noun	Adjective	Verb	Adverb
obligatory	No	Yes	No	No
mandatory	Yes	Yes	No	No

obligatory (noun)	mandatory (noun)
	a territory surrendered by Turkey or Germany after World War I and put under the tutelage of some other European power until they are able to stand by themselves
	the recipient of a mandate

obligatory (adjective)	mandatory (adjective)
morally or legally constraining or binding	required by rule
required by obligation or compulsion or convention