The sonnet (from the Italian "sonnetto" or "little song" owes much of its long-standing popularity to the Italian poet Petrarch. By the mid-sixteenth century, this fixed poetic form was adopted by the English, who borrowed the fourteen-line pattern and many of Petrarch's literary conventions. English writers did, however, alter the rhyme scheme to allow for more variety in rhyming words: while the lines of an Italian sonnet might rhyme abba, abba, cdc, dcd, an English or Shakespearean sonnet rhyme pattern might be abab, cdcd, efef, gg.

In all but three of Shakespeare's 154 sonnets ("Sonnet 99," "Sonnet 126," and "Sonnet 145"), the first three groups of four lines each are known as quatrains, and the last two lines are recognized as a couplet. The three breaks between the quatrains and the couplet serve as convenient places where the writer's train of thought can take a different direction. In "Sonnet 29," a dramatic change...