A stool is one of the earliest forms of seat furniture. It bears many similarities to a chair. It consists of a single seat, for one person, without back or armrests (in early stools), on a base of either three or four legs. A stool is generally distinguished from chairs by their lack of arms and a back. Variants exist with one, two or five legs and these various stools are referred to by some people as "backless chairs". Some modern stools have backs.