Hesychius of Alexandria , a Greek grammarian who, probably in the 5th or 6th century AD, compiled the richest lexicon of unusual and obscure Greek words that has survived, probably by absorbing the works of earlier lexicographers. The work, titled "Alphabetical Collection of All Words" (Συναγωγὴ Πασῶν Λέξεων κατὰ Στοιχεῖον), includes more than 50.000 entries, a copious list of peculiar words, forms and phrases, with an explanation of their meaning, and often with a reference to the author who used them or to the district of Greece where they were current. Hence, the book is of great value to the student of the Greek dialects, while in the restoration of the text of the classical authors generally, and particularly of such writers as Aeschylus and Theocritus, who used many unusual words, its value can hardly be exaggerated. Hesychius is important, not only for Greek philology, but also for studying lost languages and obscure dialects (such as Thracian and the ancient Macedonian language) and in reconstructing Proto-Indo-European. Many of the words that are included in this work are not found in surviving ancient Greek texts.