A sestina is a poem that consists of six stanzas of six lines each, followed by a three-line envoi. The stanzas all have the same six words at the ends of the lines, but in six different sequences that follow a specific pattern. The envoi includes all six words, usually two at the end of the lines and four in the middle.
This repeating pattern creates a sense of complexity and musicality, while also highlighting the key themes and ideas of the poem.
Here's an example of the pattern:
Stanza 1: a b c d e f
Stanza 2: f a e b d c
Stanza 3: c f d a e b
Stanza 4: b c e f a d
Stanza 5: d b a c f e
Stanza 6: e d f b c a
Envoi: (a d) e f b c