Famous sonnet writers include Petrarch, William Shakespeare, John Milton and Edmund Spenser. Each of these writers added his own variations and innovations to the sonnet, greatly influencing other writers. A sonnet is a 14-line poem, typically written in iambic pentameter and adhering to a rigid rhyme structure.
The Italian poet Petrarch is responsible for the oldest form of the sonnet. Petrarch's sonnets consisted of two stanzas: the eight-line octave and the six-line sestet. Petrarchan sonnets present an observation, argument or question within the octave and then offer a response in the sestet. These sonnets are marked by a turn in meaning, or volta, which occurs between the eighth and ninth lines. John Milton freed the Petrarchan sonnet from some of its rigid constraints, shifting its focus to more personal, interior concerns and blurring the distinction between the octave and the sestet.
William Shakespeare is responsible for the other major form of the sonnet. Shakespeare's works took a different form than Petrarch's, consisting of three four-line quatrains and a concluding two-line couplet. The ending couplet is a crucial part of the sonnet, typically offering some sort of epiphany or answer related to the previous 12 lines. Edmund Spenser took influence from Shakespeare, but shifted the formula, interweaving the rhyme scheme of the quatrains and providing linking couplets between quatrains. Spenser's sonnets also moved away from Shakespeare's revelatory ending couplets.