Greek has a documented history of 3,400 years, the longest of any single natural language in the Indo-European language family. It is also one of the earliest attested Indo-European languages, with fragmentary records in Mycenaean dating back to the 15th or 14th century BC, making it the world's oldest recorded living language. Today, it is spoken by approximately 17–25 million people in Greece (official), Cyprus (official), Albania, Bulgaria, the Former Yugoslav Republic of Macedonia (FYROM), Italy, Turkey, Armenia, Georgia, Ukraine, Moldova, Romania, Russia, Egypt, Jordan and emigrant communities around the world, including Australia, United States, Canada, Germany and elsewhere. Greek has been written in the Greek alphabet (the oldest continuously used alphabet, and the first to introduce vowels) since the 9th century BC in Greece (before that in Linear B), and the 4th century BC in Cyprus (before that in Cypriot syllabary). Greek literature has a continuous history of nearly three thousand years. Greek is a language distinguished by an extraordinarily rich vocabulary. In respect to the roots of words, ancient Greek vocabulary was essentially of Indo-European origin, but with a significant number of borrowings from the idioms of the populations that inhabited Greece before the arrival of Proto-Greeks. Words of non-Indo-European origin can be traced into Greek from as early as Mycenaean times; they include a large number of Greek toponyms. The vast majority of Modern Greek vocabulary is directly inherited from ancient Greek, although in certain cases words have changed meanings. Words of foreign origin have entered the language mainly from Latin, Italian and Ottoman Turkish. During older periods of the Greek language, loan words into Greek acquired Greek inflections, leaving thus only a foreign root word. Modern borrowings (from the 20th century on), especially from French and English, are typically not inflected.

Psycholinguistics is the psychology of language and the study of the psychological and neurobiological factors that enable humans to acquire, use, and understand language. Psycholingusitics research makes use of biology, neuroscience, cognitive science, and information theory to study how the brain processes language. There are a number of subdisciplines; for example, as non-invasive techniques for studying the neurological workings of the brain become more and more widespread, neurolinguistics has become a field in its own right.The study of word recognition and reading examines the processes involved in the extraction of orthographic, morphological, phonological, and semantic information from patterns in printed text. Psycholinguistics covers the cognitive processes that make it possible to generate a grammatical and meaningful sentence out of vocabulary and grammatical structures, as well as the processes that make it possible to understand utterances, words, text, etc. Developmental psycholinguistics studies children's ability to learn language.