Ministry translates the Greek diakonia, service, and Paul's letters use it for a wide, unfixed range of activities rather than a formal office: 1 Corinthians 12 lists prophecy, teaching, healing and administration side by side as gifts distributed through a single community, with no suggestion that only an ordained few could exercise them. The move toward a fixed structure came quickly even so.
By around the year 110, Ignatius of Antioch's letters describe bishop, presbyter and deacon as a threefold pattern every healthy congregation should have, urging obedience to the bishop in terms that assume the office already carries real authority rather than being merely one gift among others. That threefold order became the working definition of ministry across most of Christian history, Eastern and Western alike, until the Reformation reopened the question by insisting that every believer already held a priestly ministry through baptism, so that ordained ministry was a distinct function within the church rather than a different spiritual rank above it. Protestant traditions took this in different directions, some retaining bishops, others replacing them with elected elders or removing hierarchy almost entirely, but all of them widened the word ministry itself, so that lay teaching, music, and pastoral care are now routinely described as ministries in a way the earliest fixed threefold order did not anticipate.