The balalaika is a stringed

String instrument

A string instrument is a musical instrument that produces sound by means of vibrating strings. In the Hornbostel-Sachs scheme of musical instrument classification, used in organology, they are called chordophones...

 musical instrument

Musical instrument

A musical instrument is a device created or adapted for the purpose of making musical sounds. In principle, any object that produces sound can serve as a musical instrument—it is through purpose that the object becomes a musical instrument. The history of musical instruments dates back to the...

 popular in Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

, with a characteristic triangular

Triangle

A triangle is one of the basic shapes of geometry: a polygon with three corners or vertices and three sides or edges which are line segments. A triangle with vertices A, B, and C is denoted ....

 body and three strings.

The balalaika family of instruments includes instruments of various sizes, from the highest-pitched to the lowest, the prima balalaika, secunda balalaika, alto balalaika, bass balalaika and contrabass balalaika. All have three-sided bodies, spruce or fir tops, backs made of 3-9 wooden sections made usually from maple, strung usually with three strings.

The prima balalaika is played with the fingers, the sekunda and alto either with the fingers or a plectrum

Plectrum

A plectrum is a small flat tool used to pluck or strum a stringed instrument. For hand-held instruments such as guitars and mandolins, the plectrum is often called a pick, and is a separate tool held in the player's hand...

, depending on the music being played, and the basses and contrabasses (equipped with extension legs which rest on the floor) are played with leather plectrums.
The earliest mention of the term balalaika dates back to an AD 1688 Russian document.
The term "balabaika" was widely used in Ukrainian language documents from 1717-1732.