Ignatius, Bishop of Antioch, in a letter to Christians in Smyrna, in about AD 107, was the first to use the term "catholic Church" to describe catholic church signs, in its universal aspect, the undivided concretely existing Christian Church. The term "catholic Church" was soon used to distinguish this Church from heretical "Churches", as when St Cyril of Jerusalem (circa 315-386) urged those he was instructing in the Christian faith: "If ever thou art sojourning in cities, inquire not simply where the Lord's House is (for the other sects of the profane also attempt to call their own dens houses of the Lord), nor merely where the Church is, but where is the Catholic Church. For this is the peculiar name of this Holy Church, the mother of us all, which is the spouse of our Lord Jesus Christ, the Only-begotten Son of God".

The word Catholic has been used ever since to describe the one original Church founded by Christ and the Apostles, and appears in the main Christian creeds (formal definitions of belief), notably the Apostles' Creed and the Nicene Creed. As such, many Christians claim entitlement to the designation "catholic". These fall into two groups:

1) those like the Catholic, Eastern Orthodox, Oriental Orthodox Churches, and Anglican churches having Apostolic Succession from the early church; and
2) those who claim to be spiritual descendants of the Apostles but have no discernable institutional descent from the historic church, and normally do not refer to themselves as catholic.