Poetry have challenged the traditional definitions of the sonnet form, rendering entire sequences of "sonnets" that often lack rhyme, a clear logical progression, or even a consistent count of fourteen lines. "Shi" () Is the main type of Classical Chinese poetry. Within this form of poetry the most important variations are "folk song" styled verse ("yuefu"), "old style" verse ("gushi"), "modern style" verse ("jintishi"). In all cases, rhyming is obligatory. The Yuefu is a folk ballad or a poem written in the folk ballad style, and the number of lines and the length of the lines could be irregular. For the
Poetry sonnet), Michael Drayton, and Shakespeare, whose sonnets are among the most famous in English poetry, with twenty being included in the "Oxford Book of English Verse". However, the twists and turns associated with the "volta" allow for a logical flexibility applicable to many subjects. Poets from the earliest centuries of the sonnet to the present have utilized the form to address topics related to politics (John Milton, Percy Bysshe Shelley, Claude McKay), theology (John Donne, Gerard Manley Hopkins), war (Wilfred Owen, e.e. cummings), and gender and sexuality (Carol Ann Duffy). Further, postmodern authors such as Ted Berrigan and John Berryman