2 A person becomes a member of the College by virtue of Episcopal consecration and by hierarchical communion with the head of the College and with its members. Cf. n. 22, end of 1 1. In his consecration a person is given an ontological participation in the sacred functions [munera]; this is absolutely clear from Tradition, liturgical tradition included. The word "functions [munera]" is used deliberately instead of the word "powers [potestates]," because the latter word could be understood as a power fully ready to act. But for this power to be fully ready to act, there must be a further canonical or juridical determination through the hierarchical authority. This determination of power can consist in the granting of a particular office or in the allotment of subjects, and it is done according to the norms approved by the supreme authority. An additional norm of this sort is required by the very nature of the case, because it involves functions [munera] which must be exercised by many subjects cooperating in a hierarchical manner in accordance with Christ's will. It is evident that this "communion" was applied in the Church's life according to the circumstances of the time, before it was codified as law. For this reason it is clearly stated that hierarchical communion with the head and members of the church is required. Communion is a notion which is held in high honor in the ancient Church (and also today, especially in the East). However, it is not understood as some kind of vague disposition, but as an organic reality which requires a juridical form and is animated by charity. Hence the Commission, almost unanimously, decided that this wording should be used: "in hierarchical communion." Cf. Modus 40 and the statements on canonical mission (n. 24). The documents of recent Pontiffs regarding the jurisdiction of bishops must be interpreted in terms of this necessary determination of powers.
Source: Lumen Gentium (Vatican.va)