A volta is a turn or shift in a poem — a moment where the argument, tone, imagery, or perspective changes direction. The term comes from Italian (volta, turn) and is most associated with the sonnet, where it names the pivot between the octave and the sestet in the Petrarchan form, or the shift before the final couplet in the Shakespearean form.
But the volta is not confined to sonnets. Most effective poems turn somewhere: from observation to reflection, from description to address, from problem to resolution (or irresolution), from the particular to the general. The turn is what gives a poem its arc — the feeling that something has happened between the first line and the last.
A volta can be announced (by a word like but, yet, however) or unmarked, emerging only through a shift in diction, image, or rhythm. It can coincide with a stanza break or occur in the middle of a line. The best turns feel both surprising and inevitable.