In three of the pairs below the two words stand in one and the same relation, and in the fourth they do not. Mark the pair that breaks the classification.

Three of the pairs join a musical instrument to the person who plays it — the flautist to the flute, the violinist to the violin and the pianist to the piano. The odd pair gives the small flat piece of horn or plastic with which the strings are struck; the player of a guitar would have been the guitarist. The pair slips by because a plectrum belongs to the guitar as surely as a bow belongs to the violin, but the group is built on the player, not on the gear.