Hieromonk (Greek: Ἱερομόναχος, Ieromonachos; Slavonic: Ieromonakh, Romanian: Ieromonah), also called a Priestmonk, is a monk who is also a priest in the Orthodox Church and Eastern Catholicism.
A hieromonk can be either a monk who has been ordained to the priesthood, or a priest who has received monastic tonsure. In the Orthodox Church, a man must be either married or have been tonsured a monk before he is eligible for ordination; however, when a married priest's wife dies it is not uncommon for him to become a monk, since the Church forbids clergy to enter into a second marriage after ordination.
Ordination to the priesthood is the exception rather than the rule for monastics, as a monastery will usually only have as many hieromonks and hierodeacons as it needs to perform the daily services.
In the Church hierarchy, a hieromonk is of higher dignity than a hierodeacon, just as a secular (i.e., married) priest is of higher dignity than a deacon. Within their own ranks, hieromonks are assigned order of precedence according to the date of their ordination. Ranking above Hieromonk is a Hegumen and an Archimandrite.
In some countries, married clergy are referred to as "white clergy" while monastic clergy are called "black clergy" because monks should always wear black clothing but married clergy in many parts of the world typically wear white (or gray, blue or some other color) cassocks and rasons.
The proper title for a Hieromonk is, "the Reverend Hieromonk (religious name)". The form of address is, "Hieromonk (name)", "Father Hieromonk (name)", "Father (name)", or, informally, "Father". As with all Orthodox monks, a hieromonk is not addressed by his family name, but only by his religious name. In writing, if it becomes necessary to use his family name—for instance, to distinguish him from another hieromonk with the same religious name—the family name should be placed in parentheses. Example: "Hieromonk John (Smith)". In cultures where a patronymic is customary, monks are never addressed by their patronymic, but only by their religious name.
In Western Christianity, a priest who is also a monk is termed a "religious priest" or "regular clergy", i.e., living under a monastic rule (Latin: regula) .
In Roman Catholicism ordained monks are referred to as "Choir Monks" and non-ordained are called "Lay Brothers."