The mitre (British English) (/ˈmaɪtər/; Greek: μίτρα, "headband" or "turban") or miter (American English; see spelling differences), is a type of headgear now known as the traditional, ceremonial headdress of bishops and certain abbots in traditional Christianity. Mitres are worn in the Catholic Church, Orthodox Church, as well as in the Anglican Communion, some Lutheran churches, and also by bishops and certain other clergy in the Eastern Catholic Churches and the Oriental Orthodox Churches. The Metropolitan of the Malankara Mar Thoma Syrian Church also wears a mitre during important ceremonies such as the Episcopal Consecration.

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In its modern form in Western Christianity, the mitre is a tall folding cap, consisting of two similar parts (the front and back) rising to a peak and sewn together at the sides. Two short lappets always hang down from the back.

In the Catholic Church, ecclesial law gives the right to use the mitre and other pontifical insigna (crosier, pectoral cross, and ring) to bishops, abbots, and cardinals and those canonically equivalent to diocesan bishops who do not receive episcopal ordination. The principal celebrant presents the mitre and other pontifical insignia to a newly ordained bishop during the Rite of Ordination of a Bishop and to a new abbot during the Rite of Blessing of an Abbot. In the case of a person who is canonically equivalent to a diocesan bishop but does not receive episcopal ordination, this presentation normally occurs during a public installation as the ordinary of his jurisdiction. Catholic ecclesial law also permits former Anglican bishops received into full communion and subsequently ordained to the order of presbyter in the Catholic Church to obtain permission to use pontifical insignia as a mark of recognition of their previous ministry (they also may be admitted to the national or regional episcopal conference with status equivalent to that of retired Catholic bishops), but former Anglican bishops typically have not requested permission to use pontifical insignia under this provision.

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On all occasions, an altar server may wear a shawl-style veil, called a vimpa, around the shoulders when holding the bishop's mitre.

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