Final answer:
Gregorian chant is characterized by a monophonic texture, which signifies a single melodic line. The development of polyphonic genres occurred later, culminating in the Ars nova period, which contrasted with the simple texture of Gregorian chant.
Step-by-step explanation:
Gregorian chant, a significant genre of medieval music, typically has a monophonic texture. This means that it consists of a single melodic line without accompaniment or multiple voices or instruments playing different melodies simultaneously. Gregorian chants were prevalent in the liturgical practices of the medieval church. While Gregorian chant is purely monophonic, the musical texture of Western music expanded in the high medieval era, giving rise to polyphonic genres. This shift towards complexity in musical composition marked the beginning of the Ars nova period, where innovation in rhythm and notation allowed for more elaborate musical expressions, much different from the simplicity of earlier monophonic chants.