A sonnet is a fourteen-line poem in iambic pentameter. Iambic refers to the name of the foot, which is composed of a weaker syllable followed by an accented syllable. Pentameter refers to the number of feet in a line, in this case five. There are variations possible, but the basic line of a sonnet reads: Da dum da dum da dum da dum da dum with "da" being the weaker syllable and "dum" the accented syllable.

Three main sonnet forms have been in use since the Renaissance: the Italian or Petrarchan sonnet, the English or Shakespearean sonnet, and the Spenserian sonnet. Each is named for a poet who made the form famous.

Named for Francesco Petrarch, the Petrarchan sonnet is divided into an 8-line stanza, called an octave, followed by a 6-line stanza, called a sestet. This type of sonnet is constructed with a change of thought or turn between the octave and the sestet, so that the content and the form are allied. The rhyme scheme is set for the octet, but the sestet allows variants:

Octet: abbaabba

Sestet: cdecde or cdcdcd, or any combination except a scheme that ends in a rhymed couplet

The Shakespearean sonnet has three quatrains followed by a couplet, the scheme being: abab cdcd efef gg. Here, again, content is allied to form, with each stanza introducing a separate idea, extending, playing off, or arguing with what went before, the turn often coming between the final quatrain and the couplet.

Like a Shakespearean sonnet, a Spenserian sonnet has three quatrains and a couplet, and the couplet introduces new rhyme sounds to the poem. It differs, however, in that the rhyme scheme interconnects the sound of the three quatrains: abab bcbc cdcd ee. The interconnection of the three quatrains may encourage a different type of connection between them than in a Shakespearean sonnet. For example, in a sonnet by Spenser himself, each stanza is a further step in a dialogue between the speaker and the sea.