A prelate is a high-ranking member of the clergy who is an ordinary or who ranks in precedence with ordinaries. The word derives from the Latin prælatus, the past participle of præferre, which means "carry before", "be set above or over" or "prefer"; hence, a prelate is one set over others.
The archetypal prelate is a bishop, whose prelature is his particular church. All other prelates, including the regular prelates such as abbots and major superiors, are based upon this original model of prelacy.
In a general sense, a prelate in the Catholic Church and other churches and "ecclesial communities," is a bishop or other ecclesiastical person having Ordinary authority over a jurisdiction equivalent to a diocese or a similar jurisdiction (e.g. ordinariates, apostolic vicariates/exarchates, territorial abbacies). It equally applies to Cardinals (who enjoy a kind of "co-governance" of the Universal Church as the Pope's most senior ecclesiastical advisors and moral representatives) and certain "Superior Prelates of the Offices of the Roman Curia" who are not bishops, such as the auditors (judges) of the Holy Roman Rota and Protonotaries Apostolic. By extension, it refers to "inferior" or "lesser prelates," i.e. priests having the title and dress of prelates as a personal honorific, i.e. Papal Chaplains, Prelates of Honor (formerly “domestic prelates”) and honorary Protonotaries Apostolic. All these enjoy the title of monsignor (used also for bishops and archbishops, except in English-speaking countries). The seven de numero Protonotaries Apostolic in Rome, who are special papal notaries, are true prelates, like bishops; others, "supernumerary," Protonotaries Apostolic enjoy this as an honorific, like Papal Chaplains and Prelates of Honor.
Prelate, in the strict canonical sense, refers to a priest or bishop who is Ordinary of a Personal Prelature, a functional equivalent of a diocese having a “particular pastoral or missionary work for various regions or for different social groups.” (Cf. c. 294, Code of Canon Law.). At present, the only Personal Prelature in the Catholic Church is that of Opus Dei, founded by St. Josemaria Escriva de Balaguer in 1928 and raised to the status of a personal prelature in 1982. It has no territorial boundaries.
In the Armenian Apostolic (Orthodox) Church, prelate (in English) refers to a diocesan bishop, who has jurisdiction over a diocese, also called a "prelacy."