How many strings does the Indian musical instrument the sitar have?

The sitar is a plucked stringed instrument, originating from the Indian subcontinent, used in Hindustani classical music. The instrument was invented in medieval India, flourished in the 18th century, and arrived at its present form in 19th-century India. Khusrau Khan, an 18th-century figure of the Mughal Empire has been identified by modern scholarship as the inventor of the sitar.

A sitar can have 18, 19, 20, or 21 strings; 6 or 7 of these run over curved, raised frets and are played strings; the remainder are sympathetic strings ('tarb', also known as 'taarif' or 'tarafdaar'), running underneath the frets and resonating in sympathy with the played strings. These strings are generally used to set the mood of a raga at the very beginning of a presentation. The frets, which are known as 'pardā' or 'thaat', are movable, allowing fine tuning. The played strings run to tuning pegs on or near the head of the instrument, while the sympathetic strings, which have a variety of different lengths, pass through small holes in the fretboard to engage with the smaller tuning pegs that run down the instrument's neck.