The term Hexameron (Greek: Ἡ Ἑξαήμερος Δημιουργία Hē Hexaēmeros Dēmiourgia) refers either to the genre of theological treatise that describes God’s work on the six days of creation or to the six days of creation themselves. Most often these theological works take the form of commentaries on Genesis I. As a genre, hexameral literature was popular in the early church and medieval periods. The word derives its name from the Greek roots hexa-, meaning “six”, and hemer-, meaning “day”.