A gloss is an interpretive aid, and glossing represents the act of interpretation itself. A gloss can be as brief as a single word, can be a coherent set of marginal notes, or can extend to whole volumes. It is an ancient form with its roots in the Roman imperial legal system. Developing alongside changes in reading practice and scholarship, the gloss evolved extensively during the Middle Ages, reaching great significance in the early modern period during the controversies of the Reformation. The gloss can be seen as subsidiary to the main text, as a crucial adjunct to it, or as a sign of the plenitude of interpretive possibility. A gloss’ presence foregrounds literary authority, hierarchies of knowledge, and processes of meaning-making. The reader of a glossed text is placed within the creative community surrounding the work and offered a heightened sense of the temporality of reading. Recent scholarship on this form has emerged from the fields of book and reading history, but owing to the marginal status of the gloss, this scholarship also has particular affinities with structuralist and poststructuralist thought.