From the Latin mini, "lesser." The term has the same form as the Latin magister, from magis, "greater," meaning "master" or "teacher." Ministry appears in the Vulgate translation of Mt 20:26, "he who would be great [Latin, maior] among you, let him be your minister," translating the underlying Greek diakonos, "servant," as "minister." Thus ministry entered the Christian vocabulary referring to the Christian vocation to serve. Ministry refers to the work and office of the one who ministers.
In the NT, all the Corinthians ministered (Greek diakonein) to the saints in Jerusalem by their collection of the free-will offering (2 Cor 8-9). In the English language, from pre-Reformation times until the mid-twentieth century, ministry in an ecclesiastical context meant ordained ministry in its three orders. The movement of liturgical renewal and reform in the second half of the twentieth century reclaimed the earlier sense of the word, so that ministry once more denotes the life of service of all baptized persons. The Prayer Book Catechism states, "The ministers of the Church are lay persons, bishops, priests and deacons" (p. 855).