A mandolin is a stringed musical instrument in the lute family and is usually plucked.  It commonly has four sets of doubled metal strings tuned in unison, in a succession of perfect fifths.  It uses the same tuning as a violin (G3, D4,A4, E5).  It evolved in the 18th century in Italy and Germany and became popular in Europe and in the Americas in the late 19th and early 20th centuries.