The Suda (or Suida) is one of the most important lexicons of the 10th century. It contains roughly 35,000 entries, many of them from sources now unfortunately lost. The entries are arranged in alphabetical order and their explanations include etymological commentary. Its compilers used lexicographical sources, treatises, collections of ancient commentaries, proverbs, histories, biographies, philosophical texts, theological sources and literary works. Its breadth of subject matter makes the Suda a cross between a grammatical dictionary and an encyclopaedia. It is one of the most important research tools for the study of the Ancient Greek language and Ancient Greek literature.