Ancient Greek is the form of the Greek language used during the periods of time spanning the c. 9th – 6th century BC, (known as Archaic), the c. 5th – 4th century BC (Classical), and the c. 3rd century BC – 6th century AD (Hellenistic) in ancient Greece and the ancient world. It was predated in the 2nd millennium BC by Mycenaean Greek. The language of the Hellenistic phase is known as Koine (common) or Biblical Greek, while the language from the late period onward features no considerable differences from Medieval Greek. Koine is regarded as a separate historical stage of its own, although in its earlier form, it closely resembled the Classical. Prior to the Koine period, Greek of the classic and earlier periods included several regional dialects.
Ancient Greek was the language of Homer and of classical Athenian historians, playwrights, and philosophers. It has contributed many words to English vocabulary and has been a standard subject of study in educational institutions of the West since the Renaissance. This article primarily contains information about the Epic and Classical phases of the language.
The origins, early form and development of the Hellenic language family are not well understood because of the lack of contemporaneous evidence. There are several theories about what Hellenic dialect groups that may have existed between the divergence of early Greek-like speech from the common Proto-Indo-European language. They have the same general outline but differ in some of the detail. The only attested dialect from this period is Mycenaean, but its relationship to the historical dialects and the historical circumstances of the times imply that the overall groups already existed in some form.
The major dialect groups of the Ancient Greek period can be assumed to have developed not later than 1120 BC, at the time of the Dorian invasion(s), and their first appearances as precise alphabetic writing began in the 8th century BC. The invasion would not be "Dorian" unless the invaders had some cultural relationship to the historical Dorians; moreover, the invasion is known to have displaced population to the later Attic-Ionic regions, who regarded themselves as descendants of the population displaced by or contending with the Dorians.
The Greeks of this period considered there to be three major divisions of all the Greek people—Dorians, Aeolians and Ionians (including Athenians), each with their own defining and distinctive dialects. Allowing for their oversight of Arcadian, an obscure mountain dialect, and Cyprian, far from the center of Greek scholarship, this division of people and language is quite similar to the results of modern archaeological-linguistic investigation.