Full context:   Among the most common forms of poetry, popular from the Late Middle Ages on, is the sonnet, which by the 13th century had become standardized as fourteen lines following a set rhyme scheme and logical structure. By the 14th century and the Italian Renaissance, the form had further crystallized under the pen of Petrarch, whose sonnets were translated in the 16th century by Sir Thomas Wyatt, who is credited with introducing the sonnet form into English literature. A traditional Italian or Petrarchan sonnet follows the rhyme scheme A B B A , A B B A , C D E C D E , though some variation, perhaps the most common being C D C D C D , especially within the final six lines (or sestet), is common. The English (or Shakespearean) sonnet follows the rhyme scheme A B A B C D C D E F E F G G , introducing a third quatrain (grouping of four lines), a final couplet, and a greater amount of variety in rhyme than is usually found in its Italian predecessors. By convention, sonnets in English typically use iambic pentameter, while in the Romance languages, the hendecasyllable and Alexandrine are the most widely used meters.