A string instrument is a musical instrument that produces sound by vibrating strings. These instruments can be played by plucking, bowing, or striking the strings. Common examples include the violin, guitar, and cello. The pitch of the sound is determined by the string's length, tension, and thickness. String instruments are categorized into two main types: bowed and plucked. Bowed instruments, like the violin and double bass, use a bow to create sound, while plucked instruments, such as the guitar and harp, are played by directly plucking the strings with fingers or a plectrum.