What is "polychronion"

The Polychronion ( Greek: Πολυχρόνιον, "many years" or "long-lived", literally "long-timed"; ; mŭnogaja lěta) is a solemn encomium chanted in the liturgy of the Eastern Orthodox Church and those Eastern Catholic Churches which follow the Byzantine Rite.

The Polychronion is chanted for the secular authorities (Orthodox monarchs are mentioned by name, non-orthodox leaders are mentioned by title), the church authorities (the Patriarch or diocesan bishop), individuals on specific occasions, and the whole community of Orthodox Christians.