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A mandolin (Italian: mandolino pronounced [mandoˈliːno]; literally "small mandola") is a musical instrument in the lute family and is usually plucked with a plectrum or "pick". It commonly has four courses of doubled metal strings tuned in unison (8 strings), although five (10 strings) and six (12 strings) course versions also exist. The courses are normally tuned in a succession of perfect fifths. It is the soprano member of a family that includes the mandola, octave mandolin, mandocello and mandobass.

How many courses does a mandolin commonly have?
four