A sonnet is a 14-line poem that is written in iambic pentameter. The term "iambic" refers to the type of foot, or unit of rhythm, which in this case is composed of a weaker syllable followed by an accented syllable. "Pentameter" refers to the number of feet in a line, which in this case is five. Therefore, each line in iambic pentameter consists of five two-syllable units of rhythm — essentially "Da dum da dum da dum da dum da dum" in most cases, with "da" being the weaker syllable and "dum" being the accented syllable. The three traditional forms of sonnets are Italian or Petrarchan sonnets, English or Shakespearean sonnets and Spenserian sonnets.
Italian sonnets are commonly called Petrarchan sonnets, after Francesco Petrarca, a 14th-century Italian poet who was also known as Petrarch. A Petrarchan sonnet consists of an eight-line stanza, called an octave, followed by a six-line stanza, called a sestet. This type of sonnet is constructed with a change of thought or turn between the octave and the sestet, although their content and form are aligned. For example, the octave might tell of a conflict, with the sestet telling of the resolution.
The rhyming scheme of a Patrarchan sonnet is always abbaabba. In other words, the ends of fourth, fifth and eighth lines rhyme with the end of the first line, and the ends of the third, sixth and seventh lines rhyme with the end of the second. The rhyming scheme of the sestet can vary, but the final two lines do not rhyme. Most sestets in Petrarchan sonnets use a cdecde or cdcdcd rhyming scheme, but other combinations are possible, such as cddece.
English sonnets usually are called Shakespearean sonnets, after famous poet and playwright William Shakespeare, who lived in England during the late 16th and early 17th centuries. This type of sonnet has three four-line stanzas, called quatrains, followed by a two-line stanza, called a couplet. The rhyming scheme is abab cdcd efef gg. Each stanza introduces a separate idea, extending, playing off or arguing with what went before. The turn often comes between the final quatrain and the couplet.
Named after 16th-century English poet Edmund Spenser, Spenserian sonnets are variations of Shakespearean sonnets. Like a Shakespearean sonnet, it contains three quatrains followed by a couplet. Spenserian sonnets differ, however, in that their rhyming scheme interconnects the sounds of consecutive quatrains: abab bcbc cdcd ee. The interconnection of the three quatrains might encourage a different type of connection between them than in Shakespearean sonnets. For example, in one sonnet by Spenser himself, each stanza is a further step in a dialogue between the speaker and the sea.
Other forms of sonnets
There are many forms of sonnets that are variations of the traditional forms. These forms might have a different number of lines, use a different rhythmic meter or use a different rhyming scheme. For example, curtal sonnets are proportionally shorter, a caudate sonnet has extra lines at the end, and Pushkin sonnets have different meters and rhyming schemes. Occitan sonnets have two quatrains and a sestet, with the rhyming scheme being abab abab cdcdcd.