Ectenia

An Ektenia (from Greek: ἐκτενής ektenés; literally, "diligence"), often called by the better known English word litany, consists of a series of petitions occurring in the Eastern Orthodox and Byzantine Catholic liturgies. The prevalent ecclesiastical word for this kind of litany in Greek is Συναπτή (synaptê), while ektenia is the word preferred in Church Slavonic (ектенїѧ ekteniya).

A litany is normally intoned by a deacon, with the choir or people chanting the responses. As he concludes each petition, the deacon raises the end of his orarion and crosses himself; if there is no deacon serving, the petitions are intoned by a priest. During many litanies the priest says a prayer silently; after the last petition of the litany, the priest says an ecphonesis which, when a silent prayer is said during the litany, is the final phrase of that prayer.

When there is no priest present during the canonical hours, the litanies are not said; rather, the reader replaces them by saying "Lord, have mercy," three, twelve, or forty times, depending on which litany is being replaced.

The main forms of the litany are:

The Liturgy of the Presanctified Gifts contains the litanies found in the other forms of the divine liturgy, a few being altered for the context of the presanctified. One unique litany during this service is the Ektenia for Those Preparing for Illumination (i.e., for those catechumens in the final stages of preparation for baptism on Pascha).

There is also a special form of litany called a lity (Greek: Λιτή/Litê; Slavonic: Литїѧ, Litiya) which is intoned at great vespers, consisting of several long petitions, mentioning the names of numerous saints, to which the choir responds with "Lord, have mercy," many times.

...
Wikipedia