Fiend
From Marillia
In D&D and Pathfinder, a fiend is a negative supernatural entity—what we would generally call a demon.
The term is a bit weird since, again, fiends are what we'd call "demons." The term demon, however, is reserved in D&D and PF for one specific type of fiend: a Chaotic Evil race hailing from the Abyss.
Therefore, Asmodeus by this definition would not be considered a demon. He'd be a fiend—specifically a devil (a Lawful Evil fiend). This is especially weird since Asmodeus IRL is referred to as a demon.
To make matters even more confusing, you may hear various NPCs (and even me) referring to all sorts of fiends as demons. Fun.
