Scholium (tr~bXtoe), the name given to a grammatical, critical and explanatory note, extracted from existing commentaries and inserted on the margin of the manuscript of an ancient author.

Successive copyists and owners of the manuscript would alter these notes (scholiums or scholia) and in some cases they would increase to such an extent that the margin could no longer contain them, and it became necessary to make them into a separate work. At first, scholia came from one commentary only, subsequently from several. Repetition of the lemma ("catchword") may indicate this; or such phrases as "or thus", "or otherwise" or "according to some" may introduce different explanations. Tradition has identified the first scholiast as Didymus of Alexandria, and the practice of compiling scholia continued till the 15th or 16th century AD.

The word crxhXtop itself first occurs in Cicero (Ad Att. xvi. 7). The Greek scholia we possess stem mostly from anonymous writers, though the commentaries of Eustathius on Homer and Tzetzes on Lycophron form prominent exceptions. Although frequently trifling, they contain much information not found elsewhere, and have considerable value for the correction and interpretation of the text. The most important include those on:

• Homer (especially the Venetian scholia on the Iliad, discovered by Villoison in 1781 in the library of St Mark)
• Hesiod
• Pindar
• Sophocles
• Aristophanes
• Apollonius Rhodius

Prominent Latin scholia include those of:

• Servius on Virgil
• Acro and Porphyrio on Horace
• Donatus on Terence

See A. Gränhan, Geschichte der Klassischen Philologie im Altertum, iii. (1843 - 1850); WH Suringar, Historia critica scholiastarum Latinorum (1835).