A poetic form is an ordained pattern. It can be very modest: There are numerous poems consisting of one couplet. It can be quite formidable: The chant royal, a French form, is sixty lines long and turns on a mere five rhymes. A form is explicitly a bequest from the past and to write in form is to acknowledge a tie with countless others who gladly have accepted the rules that define how a certain sort of poem must be constructed. The goad of form may elicit imaginings on the poet's part that otherwise never would have occurred. A meter is a rhythmic pattern; a stanza is a unit of a particular number of lines. Prior to the twentieth century, poetry was considered to be synonymous with form. Poems were ballads and sonnets and odes and songs and blank verse narratives among other forms. The sonnet has a long pedigree that has been traced to Sicily in the thirteenth century.