Catholicism is most often used to mean Roman Catholicism, the largest Christian denomination. With this meaning, Roman Catholicism is one of Christianity’s three main branches, along with Eastern Orthodoxy and Protestantism. The Roman Catholic Church uses the term catholic to mean itself and the related Eastern Catholic Churches. Combined, these churches have a membership of approximately 1.22 billion people, or a sixth of all humanity. It is the largest religion on earth.

Salem Press Encyclopedia, 2023. 3p.