Structure
Volta
From Italian: turn. The volta is the sonnet's structural hinge; Petrarchan sonnets place it after the octave; Shakespearean sonnets often delay it until the couplet.
Definition
The turn or shift in argument, emotion, or perspective within a sonnet, typically between octave and sestet or before the closing couplet.
Example
Keats's 'When I Have Fears': the volta shifts from fearful inventory of loss to stoic 'then on the shore / Of the wide world I stand alone.'