A sestina (alsto, sextina, sestine, or sextain) is a highly structure poem consisting of six six-line stanzas followed by a tercet (called its envoy or tornada), for a total of thirty-nine lines. The same set of six words ends the lines of each of the six-line stanzas, but in a different order each time; if we number the first stanza's lines 123456, then the words ending the second stanza's lines appear in the order 615243, then 364125, then 532614, then 451362, and finally 246531. This organization is referred to as retrogradatio cruciata ("retrograde cross"). These six words then appear in the tercet as well, with the tercet's first line usually containing 1 and 2, its second 3 and 4, and its third 5 and 6 (but other versions exist, described below). English sestinas are usually written in iambic pentameter or another decasyllabic meter.