Nylon Jacket Wire

THHN
It indicates a single conductor having flame-retardant and heat-resistant thermoplastic insulation with a jacket of extruded nylon or equivalent material.
The rated operating temperature of the thermoplastic-insulated wire is 90 centigrade dry only.
THWN
It indicates a single conductor having flame-retardant, moisture and heat resistant thermoplastic insulation with a jacket of extruded nylon or equivalent material.
The rated operating temperature of the thermoplastic-insulated wire is 75 centigrade wet or dry.
THWN wire which can be exposed to mineral oil and to liquid gasoline and gasoline vapors at ordinary ambient temperature is marked with "Gasoline and Oil Resistant I" if it is suitable for exposure to mineral oil at 60 centigrade, or "Gasoline and Oil Resistant II" if suitable for exposure to mineral oil at 75 centigrade. The gasoline resistant wire has been tested at 23 centigrade when immersed in gasoline. It is considered inherently resistant to gasoline vapors within the limits of the temperature rating.