A catholicosate or catholicate is a particular ecclesiastical primacy, headed by a primate titled as a catholicos. Such regional primacies exist within various branches of Eastern Christianity, especially those of Oriental Orthodox tradition. The term catholicosate also designates the area of responsibility of a catholicos. The word is derived from the Greek Καθολικος, meaning "wholeness", and it was used to designate ecclesiastical primacy of some major metropolitan sees.