Today's Topics:

1, 2) Catechism of the Catholic Church #879 - It has a personal character and a collegial form. This is evidenced by the bonds between the episcopal college and its head, the successor of Saint Peter, and in the relationship between the bishop's pastoral responsibility for his particular church and the common solicitude of the episcopal college for the universal Church. 

http://www.scborromeo.org/ccc/para/879.htm 

The character and collegial nature of the episcopal order are evidenced among other ways by the Church's ancient practice which calls for several bishops to participate in the consecration of a new bishop. In our day, the lawful ordination of a bishop requires a special intervention of the Bishop of Rome, because he is the supreme visible bond of the communion of the particular Churches in the one Church and the guarantor of their freedom. 

www.scborromeo.org/ccc/para/1559.htm 

As Christ's vicar, each bishop has the pastoral care of the particular Church entrusted to him, but at the same time he bears collegially with all his brothers in the episcopacy the solicitude for all the Churches: "Though each bishop is the lawful pastor only of the portion of the flock entrusted to his care, as a legitimate successor of the apostles he is, by divine institution and precept, responsible with the other bishops for the apostolic mission of the Church."

http://www.scborromeo.org/ccc/para/1560.htm

Likewise, it belongs to the sacramental nature of ecclesial ministry that it have a collegial character. In fact, from the beginning of his ministry, the Lord Jesus instituted the Twelve as "the seeds of the new Israel and the beginning of the sacred hierarchy." Chosen together, they were also sent out together, and their fraternal unity would be at the service of the fraternal communion of all the faithful: they would reflect and witness to the communion of the divine persons. For this reason every bishop exercises his ministry from within the episcopal college, in communion with the bishop of Rome, the successor of St. Peter and head of the college. So also priests exercise their ministry from within the presbyterium of the diocese, under the direction of their bishop. 

http://www.scborromeo.org/ccc/para/877.htm 

https://www.catholicculture.org/culture/library/dictionary/index.cfm?id=32623

3, 4) The problem with collegiality 

https://www.angelus.online/angelus-online-january/february-2019/the-problem-with-collegiality