Petrarchan Sonnet: Structure and Rhyme Scheme

Fourteen lines, two halves

A sonnet is a 14-line poetic form. It splits into two blocks: an octave, the first eight lines, and a sestet, the last six. In the Italian tradition each line is an endecasillabo, an eleven-syllable line; the English equivalent is iambic pentameter, a ten-syllable line built on the same rise-and-fall rhythm. English poets eventually reshaped the rhyme scheme too, into a separate form known today as the Shakespearean sonnet.

That two-part structure, octave plus sestet, holds up everything else in the sonnet: the rhyme scheme and the volta discussed further down both depend on this split.

The octave’s rhyme scheme, between alternation and enclosure

In the earliest 13th-century sonnets, the octave could follow either of two schemes: alternating (ABAB ABAB) or enclosed (ABBA ABBA). The two coexisted for a few decades, until the enclosed scheme took over with the Dolce Stil Novo poets and became, in practice, the standard for the form.

Practical example: in an enclosed octave, one rhyme links the first, fourth, fifth, and eighth lines (A), while a second rhyme links the second, third, sixth, and seventh (B): A-B-B-A / A-B-B-A. The two quatrains mirror each other, instead of alternating the way ABAB ABAB does.

Francesco Petrarch, whose life and work Recaplica covers in a separate Recap on the Canzoniere, shows an almost total preference for the enclosed ABBA ABBA scheme, though a few rarer variants appear too, such as ABAB BABA or ABAB BAAB.

The tercets, looser rules

The closing tercets allow more freedom. Besides the alternating scheme (CDC DCD), documented patterns include CDD DCC, CDD CDD, CDE ECD, and CDE CDE. The last of these, with the same three rhymes repeated in the same order across both tercets, is the one Petrarch favored.

There is no single fixed recipe for the sestet, unlike the octave, where one scheme eventually pushed out the rest.

The volta, the sonnet’s hinge

Between the eighth and ninth lines, exactly where the octave gives way to the sestet, sits the volta: the moment the sonnet changes direction. In the octave the poet lays out an observation, a question, or an argument; in the sestet comes the answer, the comment, or the consequence.

From Giacomo da Lentini to Petrarch

The sonnet form began in Italy in the 1200s with Giacomo da Lentini, a poet of the Sicilian School and a notary at the court of Emperor Frederick II: tradition credits him as its inventor, and his sonnets remain the earliest known examples. Scholars still debate its exact origin: a 19th-century theory held that it was built by joining two strambotti, a popular meter of the period; the leading theory, first proposed in the 1500s, traces it instead to the canzone stanza, another verse form in use at the time. A generation later, Dante recognized Giacomo da Lentini as a master and named him in the Purgatorio, the second realm of the afterlife journey told in the Divine Comedy.

Why Petrarch’s scheme became the model

With Francesco Petrarch the sonnet stopped being just one of many short forms in the tradition and rose to the same standing as the canzone, the most prestigious meter in Italian lyric poetry. It remained the reference point throughout the 1500s, before later being adapted into other languages and traditions, each with its own rhyme schemes.