What is the difference between insulation types THW and THWN?

The primary difference between THW and THWN insulation types lies in their moisture resistance. THW (Thermoplastic Heat and Water-resistant) insulation is suitable for use in dry and wet locations but is not rated for exposure to oil or moisture. In contrast, THWN (Thermoplastic Heat and Water-resistant Nylon-coated) insulation is designed to withstand moisture and can also be used in wet locations, making it more versatile for outdoor and damp environments. Additionally, THWN insulation has a nylon coating that provides added protection against heat, abrasion, and chemicals.