Thermoplastic high-heat-resistant nylon (THHN) building wire is a coated wire typically run through conduit or cable trays. This general purpose wire is used to supply an electrical current in a range of indoor wiring projects, including control circuits and appliances. It has a durable nylon jacket that resists abrasion, protects against shock, and shields the thermoplastic insulation and metal conductor from damage.

Building wire and cable carry electrical current from a power source to a device in a building, such as an outlet or light fixture. Building wire is typically run through conduit, cable trays, or raceways. Building cable consists of multiple strands of wire bundled inside a thermoplastic or metal sheath. Building wire and cable are typically used to run new circuits or extend old circuits inside walls and ceilings in commercial, industrial, and residential properties.