A “trenta-sei” is a poetic form established by the American poet and translator John Ciardi (1916–1986). Taking its title from the Italian word for the number 36, the form consists of six six-line stanzas, rhymed ababcc. Each of the later lines in the first stanza becomes the first line of a later stanza: Line 2 is thus also line 7, line 3 is also line 13, etc. Here, for example, from 1986, is Ciardi’s “A Trenta-Sei of the Pleasure We Take in the Early Death of Keats.”

What Ciardi had in mind, no doubt, is the Italian form of the sestina. Another poetic form with six six-line stanzas (plus a concluding three-line envoi), the sestina is a difficult and tight form, with the last word of each stanza repeating as the end word of the first line of the next stanza — all while the words at the end of the first stanza’s first five lines appear in a regular pattern at the ends of other lines in the other stanzas.

It’s a difficult form to import into English (here’s Ezra Pound’s attempt, and here’s Elizabeth Bishop’s). Ciardi’s trenta-sei version eases the burden on the English poet — while keeping enough of the repetition that gives this kind of poetry its strange power. Its strange sense of song, for that matter. In today’s Poem of the Day, the Sun’s associate poetry editor, Sally Thomas (b. 1964), looks at the trenta-sei form and sees, in its claim of unity in disjointedness, the dreamlike quality that song sometimes has.

“Let’s start walking past the end,” Ms. Thomas writes, and as often in her poetry, the sense of passing time bites into the poet’s otherwise cheerful view of the world. (See, for example, other works of hers that have appeared as the Sun’s Poem of the Day: “Hindsight” and “Hawks in Holy Week”). The poem concludes, “Shadows, like the hills, are blue. / Yesterday lies where it fell. / Somewhere the last tram rings its bell.”