impervius

Impervius is a Latin adjective meaning "not to be penetrated" or "impervious." In classical usage it describes objects and materials resistant to penetration or intrusion. In modern English, the root appears in terms such as impervious and impermeable and is used to denote barriers that prevent passage of liquids, gases, or other substances.

In contemporary fiction, Impervius is most widely known as a spell in the Harry Potter series. It is the incantation for a water-repelling charm. When cast, the spell creates a temporary barrier on the target that repels water and other dampening substances, helping to keep surfaces dry. The effectiveness and duration vary with the caster’s skill. The charm is presented as a practical, classroom-level spell within Hogwarts Charms, rather than a highly advanced enchantment. A notable example occurs when Hermione Granger uses Impervius on her school books to shield them from rain.

Outside of fiction, the term impervius is rarely used as a standalone concept beyond discussions of impermeability in science or philosophy. The English cognates impervious and impermeable are more common in technical writing, but impervius remains a recognizable Latin root in literary or historical contexts.