THHN wire
a single or stranded conductor having flame-retardant and heat-resistant thermoplastic insulation with a jacket of extruded nylon or equivalent material.
 -USE: rated 90°C dry only.

THWN wire
a single conductor having flame-retardant, moisture and heat-resistant thermoplastic insulation with a jacket of extruded nylon or equivalent material.
 -USE: 75°C wet or dry.

THWN-2 wire
a single conductor having flame-retardant, moisture, and heat-resistant thermoplastic insulation with a jacket of extruded nylon or equivalent material
-USE: 90°C wet or dry.