Greek has been spoken in the Balkan Peninsula since the 2nd millennium BC. The earliest evidence of this is found in the Linear B tablets in the "Room of the Chariot Tablets", a LMII-context (c. 1500 BC) region of Knossos, in Crete. The later Greek alphabet is unrelated to Linear B, and is derived from the Phoenician alphabet (abjad); with minor modifications, it is still used today. Greek is conventionally divided into the following periods:
* Mycenaean Greek: the language of the Mycenaean civilization. It is recorded in the Linear B script on tablets dating from the 15th or 14th century BC onwards.
* Classical Greek (also known as Ancient Greek): In its various dialects was the language of the Archaic and Classical periods of Greek civilization. It was widely known throughout the Roman empire. Classical Greek fell into disuse in western Europe in the Middle Ages, but remained officially in use in the Byzantine world, and was reintroduced to the rest of Europe with the Fall of Constantinople and Greek migration to Italy.
* Hellenistic Greek (also known as Koine Greek): The fusion of various ancient Greek dialects with Attic (the dialect of Athens) resulted in the creation of the first common Greek dialect, which became a lingua franca across the Mediterranean region. Koine Greek can be initially traced within the armies and conquered territories of Alexander the Great, but after the Hellenistic colonisation of the known world, it was spoken from Egypt to the fringes of India. After the Roman conquest of Greece, an unofficial diglossy of Greek and Latin was established in the city of Rome and Koine Greek became a first or second language in the Roman Empire. Through Koine Greek is also traced the origin of Christianity, as the Apostles used it to preach in Greece and the Greek-speaking world. It is also known as the Alexandrian dialect, Post-Classical Greek or even New Testament Greek (after its most famous work of literature).
* Medieval Greek: The continuation of Hellenistic Greek during medieval Greek history as the official and vernacular language of the Byzantine Empire, and continued to be used until, and after the fall of that Empire in the 15th century. Also known as Byzantine Greek.
* Modern Greek or Romeika: Stemming independently from Koine Greek, Modern Greek usages can be traced in the late Byzantine period (as early as 11th century).
Two main forms of the language have been in use since the end of the medieval Greek period: Dhimotikí (Δημοτική), the Demotic (vernacular) language, and Katharévusa (Καθαρεύουσα), an imitation of classical Greek, which was used for literary, juridic, administrative and scientific purposes during the 19th and early 20th centuries. This diglossia problem was brought to an end in 1976 (act (νόμος) 306/1976), when Dhimotikí was declared the official language of Greece.
In the meantime, both forms of Greek had naturally converged and Standard Modern Greek (Κοινή Νεοελληνική — Common Modern Greek), the form of Greek used for all official purposes and in education in Greece today, emerged.
It has been claimed that an "educated" speaker of the modern language can understand an ancient text, but this is surely as much a function of education as of the similarity of the languages. Still, Koinē, the version of Greek used to write the New Testament and the Septuagint, is relatively easy to understand for modern speakers.
Greek words have been widely borrowed into the European languages: astronomy, democracy, philosophy, thespian, etc. Moreover, Greek words and word elements continue to be productive as a basis for coinages: anthropology, photography, isomer, biomechanics etc. and form, with Latin words, the foundation of international scientific and technical vocabulary. See English words of Greek origin, and List of Greek words with English derivatives.
Due to the long history of the Greek language, it is hard to point out specific linguistic differences between distant periods, such as "ancient", and "modern", Greek. For example the pronunciation of Beta, Gamma and Delta is commonly regarded as an important phonetic difference between Ancient and Modern periods; however evidence suggests a fricative pronunciation of Gamma as early as the 4th century BC in Boeotian, Elean, Pamphylian, and possibly even vulgar Attic, and modern pronunciation may be derived from this (this point is debated among scholars).
One way to analyse the evolution of Greek from ancient till modern times, is to view the language as a whole and examine all its four loosely defined periods simultaneously. Other scholars, however, prefer to isolate an individual, clearly (and often arbitrarily) defined period, and perhaps even a limited geographical area, then compare their results with results from other clearly defined periods in that same area.
The development from Ancient Greek to Modern Greek has affected phonology, morphology, and vocabulary.
The main phonological changes occurred during the Hellenistic and Roman period (see Koine Greek Phonology for details), and included:
* replacement of the pitch accent with a stress accent
* simplification of the system of vowels and diphthongs (loss of vowel length distinction, monophtongalization of most diphthongs, and some significant steps of iotacism)
* development of the voiceless aspirated stop consonants phi and theta to voiceless fricatives (the similar development of chi may have taken place later)
* possibly development of the voiced stop consonants — delta, beta and gamma — to voiced fricatives (the date is discussed among scholars)
The phonological changes were often not reflected in the orthography.The morphological changes affected both nouns and verbs. Some of the changes to the verbs are parallel to those that affected the Romance languages as they developed from Vulgar Latin — for instance the loss of certain historic tense forms and their replacement by new constructions — but the changes to the nouns have been less far-reaching. Greek has never experienced the wholesale loss of the nominal declension experienced by the Romance languages as they diverged from Latin. However, the phonological differences between Ancient and Modern Greek (vowel length, stress, pitch, pronunciation, etc.) do somewhat parallel those between Latin and Spanish, Portuguese, French or Italian.