Horologion (часослов; chasoslov). A liturgical book, used by precentors and singers, that contains the prayers used in daily church services. The name chasoslov is derived from the Church Slavonic word chasy (hours), which refers to the parts of the church liturgy. Besides the unchanging prayers, the Horologion contains changing liturgical hymns or chants (troparia, kontakia), paschal services, necessary instructions on ritual, and other information. The Horologion was the most popular liturgical book in old Ukraine and went through many editions. It was widely used in teaching pupils how to read, and many of its texts were memorized.
[This article originally appeared in the Encyclopedia of Ukraine, vol. 2 (1988).]