Christendom has several meanings. In a cultural sense, it refers to the religion itself, or to the worldwide community of Christians, adherents of Christianity. In its historical sense, the term usually refers to the medieval and early modern period, during which the Christian world represented a geopolitical power juxtaposed with both paganism and especially the military threat of the Muslim world. In the traditional Roman Catholic sense of the word, it refers to the sum total of nations in which the Catholic Church is the established religion of the state, or which have ecclesiastical concordats with the Holy See.