|Sonnets, and sonnet sequences, achieved their zenith in sixteenth-century in England. The Italian poet Petrarch, writing in the fourteenth century, used a form that was already a hundred years old when he composed his love poetry to Laura. He established the conventions that poets relied on for centuries thereafter: a frustrated lover, wooing an unattainable lady, compares her to such things as gardens, stars, or ships. The sometimes extravagant comparison is called a 'blazon.' By the late sixteenth century, this conceit had become so overdone that Shakespeare could parody the convention in sonnet 130: 'My mistress' eyes are nothing like the sun/Coral is far more red than her lips' red . . . ' Wyatt and Surrey composed a few early sonnets, but Sidney, Spenser, and Shakespeare perfected the form in the later "Golden Age" of the second half of the century.
This compact poem is comprised of fourteen lines of iambic pentameter and shaped most commonly by one of two rhyme schemes. The Petrarchan, or Italian sonnet is composed of an Octave, rhyming abbaabba, and a Sestet, rhyming cdecde or cdcdcd, or in some variant pattern, but with no closing couplet.
A Shakespearean sonnet, on the other hand, is divided among three quatrains and a couplet and its end rhymes follow a adad cdcd efef gg pattern.
In both types of sonnets, poetic concept parallels the rhyming blocks, so the Italian sonnet generally provides two divisions of thought and the Shakespearean four. The Italian sonnet poses one idea, sometimes a question; then with a pause, the remaining section answers or resolves the initial query or conflict. A Shakespearean sonnet often introduces a concept in the first quatrain, goes on to expand or complicate it in the second and third, and then usually concludes with a couplet that has some punch. These final two lines frequently pivot on a paradox and can completely and abruptly change the reader's mind about the sonnet's meaning.
Spenserian sonnets, or 'link sonnets,' are so called because the three quatrains are connect by a rhyme, followed by a couplet: abab bcbc cdcd ee. A final variation, the Miltonic sonnet follows the Italian form, but omits the pause between Octave and Sestet as in 'On His Blindness.'
Modern poets have varied the form further as in William Butler Yeats' 'Leda and the Swan' and Robert Frost's 'Design.' Sonnets are typically composed in iambic pentameter although other rhythms are to be found, most notably in Sidney‚s' Astrophel and Stella, whose introductory poem is composed in hexameter--six-foot lines rather than those with five feet.