Protestant vs Protestantism

Protestant and Protestantism both are nouns.

Word	Noun	Adjective	Verb	Adverb
Protestant	Yes	Yes	No	No
Protestantism	Yes	No	No	No

Protestant (noun)	Protestantism (noun)
the Protestant churches and denominations collectively	the theological system of any of the churches of western Christendom that separated from the Roman Catholic Church during the Reformation
an adherent of Protestantism

Protestant (adjective)	Protestantism (adjective)
of or relating to Protestants or Protestantism