The Shakespearean sonnet, also called the English or Elizabethan sonnet, consists of three quatrains and a final couplet. The quatrains rhyme ABAB, CDCD and EFEF, and the final couplet rhymes GG. The couplet variously summarizes the reflections in the quatrains, delivers an ironic twist at the end or looks at the same topic as the quatrains from a new perspective.
In addition to dividing a Shakespearean sonnet into quatrains and a couplet, analysts talk about its “octave” and “sestet.” The octave is the first eight lines, or two quatrains, and it introduces the poem’s topic and offers a certain view of it. The sestet is the final six lines, or the third quatrain plus the couplet. Many Shakespearean sonnets have a shift in perspective, or “volta,” as the sestet begins. For instance, Shakespeare’s Sonnet 18 begins, “Shall I compare thee to a summer’s day?” and the octave describes the problems with a summer’s day: The sun can be too hot, it’s windy, the lovely flowers eventually die. The sestet begins with a shift: “But thy eternal summer shall not fade.” The remainder of the poem suggests that the youth it addresses is superior to a summer’s day because its beauty is everlasting, immortalized in the text.