CCC 891 “The Roman Pontiff, head of the college of bishops, enjoys this infallibility in virtue of his office, when, as supreme pastor and teacher of all the faithful – who confirms his brethren in the faith he proclaims by a definitive act a doctrine pertaining to faith or morals. .. The infallibility promised to the Church is also present in the body of bishops when, together with Peter’s successor, they exercise the supreme Magisterium,” above all in an Ecumenical Council.1 When the Church through its supreme Magisterium proposes a doctrine “for belief as being divinely revealed,”2 and as the teaching of Christ, the definitions “must be adhered to with the obedience of faith.”3 This infallibility extends as far as the deposit of divine Revelation itself.4

CCC 892 Divine assistance is also given to the successors of the apostles, teaching in communion with the successor of Peter, and, in a particular way, to the bishop of Rome, pastor of the whole Church, when, without arriving at an infallible definition and without pronouncing in a “definitive manner,” they propose in the exercise of the ordinary Magisterium a teaching that leads to better understanding of Revelation in matters of faith and morals. To this ordinary teaching the faithful “are to adhere to it with religious assent”5 which, though distinct from the assent of faith, is nonetheless an extension of it.

1 LG 25; cf. Vatican Council I: DS 3074.
2 DV 10 # 2.
3 LG 25 # 2.
4 Cf. LG 25.
5 LG 25.