a celibate deacon who intends to be ordained to the priesthood
a priest-in-training, and the ordination to the diaconate is simply a pre-terminal step towards clerical completeness
a seminarian studying for the priesthood
A cleric ordained to the Sacred Order of Deacons or Diaconate, one of the three Holy Orders. Transitional Deacons share with Vocational Deacons in the identical sacrament of ordination to the Diaconate, but are ultimately called, and are in transition, to the ministry of priesthood.
In the Roman Catholic church, a transitional deacon is a celibate man who has been ordained a deacon and who intends to become a priest. For several centuries, all Roman Catholic deacons were in this transitional stage between layman and priest. The role of permanent deacon, usually a married man who is unable to remarry after ordination if his wife predeceases him, was revived after the Second Vatican Council in the 1960s.