The Leiden Conventions or Leiden system is an established set of rules, symbols, and brackets used to indicate the condition of an epigraphic or papyrological text in a modern edition.
In previous centuries of classical scholarship, scholars who published texts from inscriptions, papyri, or manuscripts used divergent conventions to indicate the condition of the text and editorial corrections or restorations.
The Leiden meeting was designed to help to redress this confusion.
The earliest form of the conventions was agreed at a meeting of classical scholars at the University of Leiden in 1931 and published the following year.
More recently, scholars have published improvements and adjustments to the system.