noun
also ca·this·ma ˈkȧthēzmə
( plural kathisma·ta kȧˈthēzmətə)
Etymology: Middle Greek kathisma, from Greek, sinking, settling down, from kathizein to seat, sit down, from kata- cata- + hizein to seat; akin to Greek hezesthai to sit — more at sit
: one of the 20 sections into which the Psalter is divided for liturgical use in the Eastern Orthodox Church