Ancient Greek is the form of Greek used during the periods of time spanning c. the 9th – 6th century BCE (known as Archaic), c. the 5th – 4th century BCE (Classical), and c. the 3rd century BCE– 6th century CE (Hellenistic) in ancient Greece and the ancient world.
It was predated in the 2nd millennium BCE 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 English vocabulary words and has been a standard subject of study in educational institutions of the West since the Renaissance.