Another closely related form is the " fourteener ", consisting of iambic heptameter couplets : instead of alternating lines of iambic tetrameter and iambic trimeter, rhyming " a-b-a-b " or " x-a-x-a ", a fourteener joins the tetrameter and trimeter lines, converting four-line stanzas into couplets of seven iambic feet, rhyming " a-a ".
