One foot is equivalent in length to 12 inches or one-third of a yard. The foot is a unit of measure for length and distance.
The plural version of foot is written as feet. This unit of measurement is abbreviated as ft or '. For example, 10 feet can be written as either 10 ft or 10'.
The foot is used primarily in the United States customary measurement systems, but it can be found in use worldwide. It is the unit of measure for altitude in the aviation industry.
Historically, the foot's origin was being the length of an adult male's foot.