Villanelle
Rules quoted from the poets.org glossary; examples only from public-domain poems.
The rules, quoted
The villanelle is a highly structured poem made up of five tercets followed by a quatrain, with two repeating rhymes and two refrains.
The first and third lines of the opening tercet are repeated alternately in the last lines of the succeeding stanzas; then in the final stanza, the refrain serves as the poem’s two concluding lines.
A1 b A2 / a b A1 / a b A2 / a b A1 / a b A2 / a b A1 A2 .
Our explanation written by Tale of the Muse
A villanelle is five tercets and a closing quatrain, nineteen lines by our count, built on two rhymes and two refrains. Lines one and three of the opening tercet return in turn as the last line of each tercet that follows, and both come back together to end the poem, which is what the pattern A1 b A2 records.
Our plain-language restatement of the glossary rules above. It adds no facts of its own.
Example
No public-domain example is shown for this form.