Are notes on a text, normally substantial sets of explanatory and critical notes written in the margin or between the lines of manuscripts. Many of them go back to ancient commentaries (which might fill volumes of their own). Scholia result from excerption, abbreviation, and conflation, brought about partly by readers' needs and partly by lack of space.
Like their modern successors, ancient commentators sometimes guessed or talked nonsense, but at their best scholia are a mine of information, though less in Latin than in Greek. Aristophanes benefits most, because explanation of topical or literary references and allusions began at Alexandria in the heyday of the Library.
Subjects: Classical Studies.