It may also be used strictly to refer to poems in the styles of the Confucian classic, regardless of their time of composition. Owing to the variety of pieces included in the Classic, there are few formal constraints apart from line length (usually four characters and no more than seven) and rhyming every other line.
Jintishi, literally "Modern Poetry", was actually composed from the 5th century onwards and is considered to have been fully developed by the early Tang dynasty. The works were principally written in five- and seven-character lines and involve constrained tone patterns, intended to balance the four tones of Middle Chinese within each couplet. The principal forms are the four-line jueju, the eight-line lüshi, and the unlimited pailü. In addition to the tonal patterns, lüshi and pailü were usually understood to further require parallelism in their interior couplets: a theme developed in one couplet would be contrasted in the following one, usually by means of the same parts of speech.