excursus

An excursus is a digression or extended aside within a work of literature, philosophy, history, or criticism. It comprises a self-contained discussion that diverges from the main narrative or argument but remains connected to it by relevance or interest.

In practice, an excursus provides background, theoretical justification, or historical context. It may elaborate on a methodology, linguistic analysis, geography, or biographical details, offering depth without derailing the main argument. It can also anticipate counterarguments or demonstrate the breadth of the author's knowledge.

The term is of Latin origin, from excursus, the past participle of excurrere, meaning to run out or to go forth. In English, excursus is used primarily in scholarly writing; the plural excursuses is rare, with excursūs also attested in some sources. It is distinct from a digression or an aside in that it tends to be more planned and relatively substantial, often integrated into the text's architecture.

In contemporary usage, excursuses appear in long-form essays, scholarly monographs, and some historical novels, where an author includes a substantial interlude to develop related ideas before returning to the main thread. See also: digression, aside, appendix.