What is the criterion underlying the periodization of the Middle Ages?

The era of the Middle Ages can be roughly divided into the following periods:

Early Middle Ages – covers the period from the 5th to the 11th century;

Classical Middle Ages – takes the period from the 11th to the 14th century;

Late Middle Ages – covers the time from the 14th to the 15th century.

Thus, we can say that the Middle Ages was divided into three stages, each of which was characterized by certain specific features.