A tercet is a stanza or poem made up of three lines of poetry.
The term describes a structural unit rather than one fixed rhyme scheme. A tercet may be unrhymed, or its three lines may follow patterns such as AAA or ABA. Because the form is compact, poets often use it to create a sharp image, complete a brief thought, or give a passage a measured rhythm.
One well-known type is the enclosed tercet, which commonly uses an ABA rhyme pattern. Another is terza rima, the interlocking form associated with Dante Alighieri’s “Divine Comedy.” In terza rima, the middle rhyme of one tercet connects with the outer rhymes of the next, producing a chain such as ABA BCB CDC.
A tercet can stand alone as a complete short poem, and English-language haiku is often presented as an unrhymed three-line poem. The word should not be confused with “triplet,” which usually refers to three successive lines sharing the same rhyme, often an AAA pattern. A couplet has two lines, a quatrain four, and a sestet six.