An umbrella or parasol is a folding canopy supported by wooden or metal ribs that is mounted on a wooden, metal, or plastic pole. It is usually designed to protect a person against rain. The term umbrella is traditionally used when protecting oneself from rain, while parasol is used when protecting oneself from sunlight, though the terms continue to be used interchangeably. Often the difference is the material used for the canopy; some parasols are not waterproof, and some umbrellas are transparent. Umbrella canopies may be made of fabric or flexible plastic. There are also combinations of parasol and umbrella that are called en-tout-cas.