Roman grammarian. Active in the 2nd century.
Festus edited an abridged version of a Latin etymological dictionary, De verborum significatu ("On the meaning of words"), originally written by Marcus Verrius Flaccus in the beginning of the 1st century.
Flaccus' original work is now lost, but of the 20 scrolls of Festus' abridged version, the 12th-20th volumes survive (beginning with the letter M).
As a source for archaic and classical Latin, and for insight into the working methods of Roman philologists, Festus is irreplaceable.