A vital dimension of being Catholic is accepting the totality of the Church’s doctrine. This is the only way of guaranteeing that Catholics are bound together ‘as a whole’.
Therefore, ‘Catholic’ refers to those who accept the universal faith of the Church, as opposed to those who accept only part of it.
Communionwith Rome is an essential part of Catholicity. One is a ‘Catholic’ who accepts the wholeness of the Christian faith as expressed in that fullness of communion with the Bishop of Rome, the Successor of Peter.
The See of Rome, in communion with the whole Church, has articulated the full profession of faith through the Catechism of the Catholic Church, which ‘aims at presenting an organic synthesis of the essential and fundamental contents of Catholic doctrine, as regards both faith and morals’ (CCC 11).