What is the defining characteristic of a sonnet?

The defining characteristic of a sonnet is that it is a 14-line poem with a specific rhyme scheme. This form has its roots in Italian poetry, particularly with poets like Petrarch, and was later adapted by English poets such as Shakespeare and Spenser. The structure generally includes a specific number of syllables per line, typically iambic pentameter, and adheres to certain rhyme patterns, which can vary depending on the type of sonnet—such as the Petrarchan (or Italian) sonnet, which typically features an octave and a sestet, and the Shakespearean (or English) sonnet, which consists of three quatrains followed by a couplet.

In contrast, a long narrative poem is associated with forms such as epics, and free verse typically eschews consistent meter or rhyme patterns entirely, which is at odds with the prescribed structure of sonnets. A verse drama in five acts refers to a format used in playwriting, notably by Shakespeare and other playwrights, which also diverges significantly from the characteristics typical of a sonnet. Understanding these distinctions aids in recognizing the unique place of sonnets within the broader category of poetry.