A villanelle is a nineteen line poem with a strict rhyme scheme. It consists of five tercets with two lines repeating throughout and ending the poem. The first and third lines of the first tercet repeat alternately until the end. Sylvia Plath's "Mad Girl's Love Song" is provided as an example. The structure requires lines ending in rhyming words A and B to repeat in a specific pattern. To write a villanelle, choose rhyming words and two repeating lines, then fill in the structure ensuring the rhyme pattern is followed. The villanelle form can also be applied to music by repeating phrases and rhyming the last bars in the same pattern.