Ancient Greek: in its various dialects, the language of the Archaic and Classical periods of the ancient Greek civilization. It was widely known throughout the Roman Empire.

Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (c. 1400–1200 BC), Dark Ages (c. 1200–800 BC), the Archaic or Epic period (c. 800–500 BC), and the Classical period (c. 500–300 BC).

The Proto-Greek language (also known as Proto-Hellenic) is the Indo-European language which was the last common ancestor of all varieties of Greek, including Mycenaean Greek, the subsequent ancient Greek dialects (i.e., Attic, Ionic, Aeolic, Doric, Arcadocypriot, and ancient Macedonian —either a dialect or a closely related Hellenic language) and, ultimately, Koine, Byzantine and Modern Greek (along with its variants).