The AA battery is a standard size single cell cylindrical dry battery. The IEC 60086 system calls it size R6, and ANSI C18 calls it size 15. It is named UM-3 by JIS of Japan. Historically, it is known as D14 (standard cell) or HP7 (for zinc chloride 'high power' version) in official documentation in the United Kingdom.
AA batteries are common in portable electronic devices. An AA battery is composed of a single electrochemical cell that may be either a primary battery (disposable) or a rechargeable battery. Several different chemistries are used in their construction. The exact terminal voltage, capacity and practical discharge rates depend on cell chemistry; however, devices designed for AA cells will usually only take 1.2-1.5 V unless specified by the manufacturer.
Introduced in 1907 by The American Ever Ready Company, the AA battery size was standardized by the American National Standards Institute (ANSI) in 1947, but it had been in use in flashlights and electrical novelties before formal standardization. ANSI and IEC Battery nomenclature gives several designations for cells in this size, depending on cell features and chemistry. Due to their popularity in small flashlights, they are often called "penlight batteries".