THWN is a type of electrical cable that stands for Thermoplastic Heat and Water-resistant Nylon-coated. Some synonyms for THWN include THHN, TFFN, and MTW. THHN is a similar type of wire that is commonly used for general-purpose wiring and is often used interchangeably with THWN. TFFN stands for Thermoplastic Flexible Fixture Nylon and is used in applications that require flexibility, such as lighting fixtures. MTW, or Machine Tool Wire, is a type of THWN wire that is specifically designed for use in machines and equipment. While these wires have slight variations, they all share the common characteristic of being heat and water-resistant, making them ideal for electrical applications.