Gregory vs Gregorian

Gregory is a noun but Gregorian is not a noun.

Word	Noun	Adjective	Verb	Adverb
Gregory	Yes	No	No	No
Gregorian	No	Yes	No	No

Gregory (noun)	Gregorian (noun)
(Roman Catholic Church) an Italian pope distinguished for his spiritual and temporal leadership; a saint and Doctor of the Church (540?-604)
the Italian pope who fought to establish the supremacy of the pope over the Roman Catholic Church and the supremacy of the church over the state (1020-1085)
the Italian pope from 1406 to 1415 who worked to end the Great Schism and who retired to make it possible (1327-1417)
the pope who sponsored the introduction of the modern calendar (1572-1585)
Italian pope from 1831 to 1846; conservative in politics and theology; worked to propagate Catholicism in England and the United States (1765-1846)
(Roman Catholic Church) a church father known for his constant fight against perceived heresies; a saint and Doctor of the Church (329-391)

Gregory (adjective)	Gregorian (adjective)
	of or relating to Pope Gregory I or to the plainsong chants of the Roman Catholic Church
	of or relating to Pope Gregory XIII or the calendar he introduced in 1582