Metre (poetry) of over some two-and-a-half millennia. Beginning with the earlier recorded forms: the Classic of Poetry tends toward couplets of four-character lines, grouped in rhymed quatrains; and, the Chuci follows this to some extent, but moves toward variations in line length. Han Dynasty poetry tended towards the variable line-length forms of the folk ballads and the Music Bureau yuefu. Jian'an poetry, Six Dynasties poetry, and Tang Dynasty poetry tend towards a poetic metre based on fixed-length lines of five, seven, (or, more rarely six) characters/verbal units tended to predominate, generally in couplet/quatrain-based forms, of various total verse lengths. The Song poetry
Tercet in the 16th century. It was employed by Shelley and is the form used in Byron's "The Prophecy of Dante". Tercet A tercet is composed of three lines of poetry, forming a stanza or a complete poem. English-language haiku is an example of an unrhymed tercet poem. A poetic triplet is a tercet in which all three lines follow the same rhyme, AAA; triplets are rather rare; they are more customarily used sparingly in verse of heroic couplets or other couplet verse, to add extraordinary emphasis. Other types of tercet include an enclosed tercet where the lines rhyme in an