Greek dialects are variations of the Greek language that developed in different regions of Greece and surrounding areas. The main dialects include Attic, Ionic, Doric, and Aeolic, each with unique features in vocabulary, pronunciation, and grammar. These dialects were prominent in ancient times and influenced the development of Koine Greek, which became the common language of the Hellenistic world. Over time, the Greek language evolved, and many of these dialects faded or merged. Today, modern Greek is primarily based on Demotic Greek, but some regional dialects still exist, reflecting the rich linguistic history of the Greek-speaking world.