The villanelle is an intricate poetic form consisting of five or more three-line stanzas (tercets) and a final four-line stanza (quatrain), all relying on only two rhymes. The first and third lines of the poem alternate as the last lines of the three-line stanzas, and together end the quatrain. This exacting form is chiefly used in Medieval French poetry, although a few poets writing in English have used it. One is W.H. Auden, who wrote a villanelle that is sometimes also called "If I Could Tell You", and Dylan Thomas, whose "Do Not Go Gentle" is a well-known example.