Ballads were originally written to accompany dances, and so were composed in couplets with refrains. Most northen and west European ballads are written in ballad stanzas or quatrains (four-line stanzas) of alternating lines of iambic tetrameter (eight syllables) and iambic trimeter (six syllables), known as ballad meter.
Chiara Colombu, 5ª A Linguistico 2017-18