To me, any handgun is a pistol, single shot, revolver, or semi.
"Handgun" is the super category. "Revolver" and "pistol" are subcategories underneath it in the same way that "chicken" is the super category, underneath which falls "hen" and "rooster." Not all chickens are roosters, and not all handguns are revolvers. Similarly, not all chickens are hens, and not all handguns are pistols.
