A type of fixed form poetry consisting of nineteen lines of any length divided into six stanzas: five tercets and a concluding quatrain. The first and third lines of the initial tercet rhyme; these rhymes are repeated in each subsequent tercet (aba) and in the final two lines of the quatrain (abaa). Line 1 appears in its entirety as lines 6, 12, and 18, while line 3 reappears as lines 9, 15, and 19. Dylan Thomas’s "Do not go gentle into that good night" is a villanelle. See also fixed form, quatrain, rhyme, tercet.