Acolouthia, (from the Greek: akoloutheo, "to follow"; Slavonic: posledovanie) in the Eastern Orthodox churches, signifies the arrangement of the Divine Services (Canonical Hours or Divine Office), perhaps because the parts are closely connected and follow in order. In a more restricted sense, the term "acolouth" refers to the fixed portion of the Office (that which does not change from day to day). The portions of the Office that are variable are called the Sequences. While the structure and history of the various forms of the Divine Office in the numerous ancient Christian rites is exceedingly rich, the following article will restrict itself to the practice as it evolved in the Eastern Roman (Byzantine) Empire.