An Afterfeast is a period of celebration attached to one of the Great Feasts celebrated by the Orthodox Christian and Eastern Catholic Churches (somewhat analogous to what in the West would be called an Octave).
The celebration of the Great Feasts of the church year are extended for a number of days, depending upon the particular Feast. Each day of an Afterfeast will have particular hymns assigned to it, continuing the theme of the Feast being celebrated. At each of the divine services during an Afterfeast, the (Gk.) troparion and (Gk.) kontakion of the feast are read or chanted. The (Gk.) canon of the feast will usually be chanted on every day of the Afterfeast (if two canons were chanted on the day of the feast, they will be alternated on the days of the afterfeast). Some of the Great Feasts of the Lord will have a special canon composed of only three odes, called a (Gk.) Triode, which will be chanted at Compline on each day of the Afterfeast.
Most of these Great Feasts also have a day or more of preparation called a Forefeast (those Feasts that are on the moveable Paschal Cycle do not have Forefeasts). Forefeasts and Afterfeasts will affect the structure of the services during the Canonical Hours.
The last day of an Afterfeast is called the Apodosis (Gk. "leave-taking", lit. "giving-back") of the Feast. On the Apodosis, most of the hymns that were chanted on the first day of the Feast are repeated. On the Apodosis of Feasts of the Theotokos, the Epistle and Gospel from the day of the Feast are repeated again at the Divine Liturgy.
The Forefeasts and Afterfeasts break down as follows: