A stool is a simple seat without a back or arms, usually supported by legs. You might sit on a stool at a kitchen counter while eating breakfast, or perch on one at a piano while practicing scales. Bar stools line restaurant counters, and lab stools help scientists work at tall tables. A footstool is a small, low stool you rest your feet on while sitting in a chair.

Stools are one of the oldest types of furniture, used for thousands of years precisely because they're so straightforward to build. A three-legged stool (often called a milking stool) stays steady even on uneven ground, which is why farmers used them in barns. Their lack of a back makes stools easy to tuck under tables and move around.

The word can also mean something completely different: doctors and nurses use “stool” as a medical term for feces, the solid waste that leaves your body. When a doctor orders a stool sample, they're checking it for signs of health problems.