Common metre or common measure—abbreviated as C. M. or CM—is a poetic metre consisting of four lines that alternate between iambic tetrameter (four metrical feet per line) and iambic trimeter (three metrical feet per line), with each foot consisting of an unstressed syllable followed by a stressed syllable. The metre is denoted by the syllable count of each line, i.e. 8.6.8.6, 86.86, or 86 86, depending on style, or by its shorthand abbreviation "CM". Common metre has been used for ballads such as "Tam Lin" and hymns such as "Amazing Grace" and the Christmas carol "O Little Town of Bethlehem". The upshot of this commonality is that lyrics of one song can be sung to the tune of another; for example, "Advance Australia Fair", "House of the Rising Sun", Pokémon Theme and "Amazing Grace" can have their lyrics set to the tune of any of the others. Historically, lyrics were not always wedded to tunes and would therefore be sung to any fitting melody; "Amazing Grace", for instance, was not set to the tune "New Britain" (with which it is most commonly associated today) until fifty-six years after its initial publication in 1779. Variants Common metre is related to other poetic forms. Ballad metre Like common metre, ballad metre comprises couplets of tetrameter (four feet) and trimeter (three feet). However, the feet need not be iambs (with one unstressed and one stressed syllable): the number of unstressed syllables is variable. Ballad metre is "less regular and more conversational" than common metre. In each stanza, ballad form typically needs to rhyme only the second lines of the couplets, not the first, in the form A-B-C-B (where A and C need not rhyme), while common metre typically rhymes both the first lines and the second lines, in the pattern A-B-A-B. Fourteener The fourteener is a metrical line of 14 syllables (usually seven iambic feet). Fourteeners typically occur in couplets. Fourteener couplets broken into quatrains (four-line stanzas) are equivalent to quatrains in common metre or ballad metre: instead of alternating lines of tetrameter and trimeter, a fourteener joins the tetrameter and trimeter lines to give seven feet per line. The fourteener gives the poet greater flexibility than common metre, in that its long lines invite the use of variably placed caesuras and spondees to achieve metrical variety, in place of a fixed pattern of iambs and line breaks. Common-metre double and particular Another