The sonnet, like the limerick, is an example of a fixed or ‘closed' form because its defining characteristics are largely formal. The sonnet is a fourteen-line poem in iambic pentameter with a complex rhyme scheme which divides the fourteen lines into smaller groups that correspond with stages in the poem's argument, rhetoric or internal reflection. The change in the rhyme scheme between octave and sestet is accompanied ‘nearly always by a break in syntax and thought at the “turn”. The sonnets about or addressed to the ‘dark lady' – deeply ambivalent about her and about sex – are very different to those addressed to the young man. The last major English poet to write sonnets before it went into cold storage for a hundred years or more was Milton, who wrote twenty-three occasional sonnets on various subjects.