What is "tetraevangelion"

Tetraevangelion (, "Four Evangelia/ Gospel Books"; Old Slavonic: благовѣствованиѥ; ) is a name used in Eastern Orthodox terminology for the Canonical gospels of the Four Evangelists. Examples of notable medieval manuscripts include:

• Gospels of Tsar Ivan Alexander (1355–56), Bulgarian, illuminated.
• Jakov of Serres' (1354), Serbian, illuminated.
• Vani Gospels (12–13th c.), Georgian, illuminated.
• Mstislav Gospel (12th c.), Russian, illuminated.
• Codex Marianus (11th c.), South Slavic. One of the oldest Slavic tetraevangelion.
• Codex Zographensis (10–11th c.), South Slavic, illuminated. Oldest Slavic tetraevangelion.