The villanelle consists of five stanzas of three lines (tercets) followed by a single stanza of four lines (a quatrain) for a total of nineteen lines.[7] It is structured by two repeating rhymes and two refrains: the first line of the first stanza serves as the last line of the second and fourth stanzas, and the third line of the first stanza serves as the last line of the third and fifth stanzas.[7] The rhyme-and-refrain pattern of Do not go gentle into that good night can be schematized as A1bA2 abA1 abA2 abA1 abA2 abA1A2 where letters ("a" and "b") indicate the two rhyme sounds, upper case indicates a refrain ("A"), and superscript numerals (1 and 2) indicate Refrain 1 and Refrain 2.