One of the Indo-European languages, brought to Greece by the Achaeans around 1700 BC. Originally there were a variety of spoken dialects, most notably Ionic, Doric, and Attic. Attic Greek was the language of Athens; most of the surviving classical Greek literature is in Attic Greek. Alexander the Great, besides being a great military leader, was instrumental in combining these dialects to form Classical Greek. During the Hellenistic period, a mixing of peoples led to the development of a common form called koinê - the language in which the New Testament was originallly written. From this descended the Greek that was the official language of the Byzantine Empire and finally the modern Greek of today. The earliest written version of the Greek language is known as Linear B.
Greek is famous for its ability to precisely specify syntax - for instance, it has a full 24 forms in the declension of the definite article (4 cases, 3 genders, 2 numbers):
SINGULAR PLURAL Masc. Fem. Neuter Masc. Fem. Neuter Nominative (subject) o ê to oi ai ta Genitive (possessive) tou tês tou tôn tôn tôn Dative (indirect object+) tô tê tô tois tais tois Accusative (direct object) ton tên to tous tas ta
A large of number of words in English, Latin, and so forth, come from Greek.