col arco
With the bow; an instruction to resume bowing after pizzicato.
In Depth
Col arco means with the bow and is an instruction for string players to return to normal bowing after a passage using a different technique, most commonly pizzicato. Since bowing is the default way of playing string instruments, col arco only appears when a change back is needed.
The instruction can also appear after col legno passages. Players need a moment to reposition the bow correctly when switching between techniques, so composers typically place the marking slightly ahead of where the bowing should begin.
In Bartók's Music for Strings, Percussion and Celesta, the transition from pizzicato to arco is used as a structural turning point that divides the entire piece.