Bref double is a French poetic form consisting of 3 quatrains and a final couplet, making 14 lines. There is some debate about the rhyme scheme, though in all versions the scheme consists of three rhymes and 4-5 un-rhymed lines, providing the bref double's primary distinction from sonnets. According to Lyon, the bref double has a single form with a fixed rhyme scheme and, most distinctively, only the first two quatrains share a final rhyme: axbcxaxcaxabab axbcxaxcbxxcab However, other variants are possible, such as: axxbcxxbacxbac