errant

Errant is an adjective in English that describes wandering or roving movement, or a departure from a proper or expected course. It can refer to physical motion, such as an errant traveler who loses their way, or to behavior that deviates from established standards, rules, or goals. The term can also function as a noun in historical or literary contexts, notably in the compound knight-errant, which designates a medieval knight who travels in search of adventure and to right wrongs.

Etymology and sense development: Errant derives from Old French errant and from Latin errare, meaning to wander. The core sense remains the notion of wandering, with extended use to describe deviations—be they literal trajectories, like an errant missile or satellite, or figurative paths, such as an errant policy or errant conduct. The word often carries a hint of literary or formal tone, particularly in phrases like knight-errant or errant arc of a journey.

Usage notes: In modern prose, errant describes both literal wandering and deviation from a planned course. It can appear in journalism, science, and fiction to signal that something has strayed from its intended target or purpose. As a noun, its usage is largely historical or stylistic, with knight-errant as the most familiar form. While related terms include stray, rogue, and erroneous, errant emphasizes movement or deviation rather than simply fault or falsity.