A sonnet (It. sonetto, “little song”) is a piece of lyric verse consisting of fourteen ten- (in English), eleven- (in Italian), or twelve- (in French) syllable lines, with rhymes arranged according to one or another definite scheme.

Because of its mathematical structure, there is a technical numerological vocabulary for discussing the parts of the sonnet form. Because poets must think about how to form their language in these terms, it is important to talk about the language in these terms.

A quatrain is a stanza of four lines. Often two quatrains comprise an octave.

An octave is a group of eight lines, usually two quatrains. Most often, the octave is the first eight lines of a sonnet.

A tercet is a group of three lines. In the Italian sonnet, two tercets often comprise a sestet.

A sestet is a group of six lines. Most often, the sestet is the last six lines of a sonnet (two tercets in the Italian Sonnet; a quatrain and a couplet in an English Sonnet).

A couplet is a group of two lines, often the last two lines of an English or Spenserian sonnet.

There are three popular sonnet forms: the Italian or Petrarchan, the Spenserian, and the English or Shakespearean.

The Italian sonnet, sometimes called the Petrarchan sonnet, has an octave rhyming abba abba, and a sestet usually rhyming cdcdcd or cdecde.

The Spenserian sonnet has the rhyme scheme abab bcbc cdcd ee.

The English sonnet, sometimes called the Shakespearean sonnet, has the rhyme scheme abab cdcd efef gg.

Properly, a sonnet expresses one main idea (the conceit), but conventionally the sonnet came to express an initial idea (the conceit) and a turn (the volta) to something else, or a problem and an answer.

The conceit is the central concept, notion, idea, or thought in a sonnet, often an observation, paradox, or metaphor. In sonnets with a volta, the conceit can be thought of as “the problem.”

A musical term for a turn, a volta is a point of transition, either grammatically or conceptually. Gramatically, a volta might be a turn from the octave to the sestet. Conceptually, a volta can be thought of as “the answer” to “the problem.” Often the grammatical and conceptual breaks come together, but not always. When they do not come together, it is important to ask if the turn is really a turn after all.

Sometimes sonnets appear in a prosimetrum, a work that alternates between prose and verse. This work was originally formed when a sonneteer would look back, older and wiser, and narrate what made him write the sonnets of his youth. Thus he reprints a sonnet, then explains its meaning, then reprints another, and explains again. As such, the prosimetrum is one of the first forms of literary criticism, all the more impressive because it is a literary criticism of one’s own poetry. Additionally, the prosimetrum establishes the peculiar habit of looking for the story behind the poem when we read a sonnet. That is, the prosimetrum treats the sonnet as a picture in time, like a still-frame from a film.

Arranging sonnets in a prosimetrum led sonneteers to start writing them as parts of a narrative, called a sonnet sequence.

Because the sonnet form was so commonly used for love poetry in its early days, it came to be the form poets used to express erotic thought in verse.

When a writer choses to use the sonnet form, there is always the implication of an erotic relationship, even if it is between two heterosexual males or a human and a god. To be “erotic” is not necessarily to be sexual. To be “erotic” is to express desire, as opposed to reason, truth, conscience, or any other wet blanket on our unadulterated passions.

The eroticism of the sonneteer was understood to be very facile early in the sonnet tradition. Thus, “the sonnetter” became a character of sorts, usually a naïve young man whose erotic expectations for the world are violated by his experience in that world. That is, there is hardly ever a time when a sonnet is not ironic, when a sonnet is not “feigning ignorance” of the immature attitudes ascribed to the sonneteer. Thus, some very sophisticated poets take on the persona of an unsophisticated sonneteer in order to explore the origins and exigencies of desire.