A kathisma, literally, "seat", is a division of the Psalter, used in the Eastern Orthodox and Byzantine Rite Catholic churches. The word may also describe a hymn sung at Matins, a seat used in monastic churches, or a type of monastic establishment.

A psalter is a volume containing the Book of Psalms, often with other devotional material bound in as well, such as a liturgical calendar and litany of the Saints. Until the emergence of the book of hours in the Late Middle Ages, psalters were the books most widely owned by wealthy lay persons. They were commonly used for learning to read. Many Psalters were richly illuminated, and they include some of the most spectacular surviving examples of medieval book art.