Written in a sequence and addressed to the object of the poet's passion, Shakespeare's sonnets follow the English sonnet form with its three four-line quatrains plus a concluding two-line couplet are used to trace the development of this relationship of the poet and his lover. More commonly known as the Shakespearean sonnet, the rhyme scheme [regular pattern of rhyming words] is as follows:abab cdcd efef gg. Each of the three quatrains explores a different variation of the theme and the rhyming couplet presents a summarizing or concluding statement on this theme. For instance, the first quatrain of Sonnet 18 presents the rhetorical question of comparing the lover to a summer's day. The poet declares that the lover is "more lovely and more temperate," and he demonstrates the truth of his statement. In what is known as a volta, or turn in thought, the second quatrain explains how Nature is sometimes too severe and beauty is destroyed. Then, in the third quatrain, the poet continues his argument that the object of his passion will possess eternal beauty because the sonnet itself will attest to her beautyl: "But thy eternal summer shall not fade," the poet declares as the lover will live on in his verse. Finally, the rhyming couplet concludes by reiterating the theme that the sonnet itself will render the love eternal. Thus, the rhyme scheme controls the thematic development of the sonnet.
The meter of the Shakespearean sonnet, or its rhythmical pattern is iambic pentameter. That is, there is a foot with one unstressed syllable follwed by one stressed syllable as in the word afraid [a is unstressed, fraid is stressed]. Five of these feet makes the pentameter. For instance, "Shall I compare thee to a summer's day?" which is the first line, exhibits this iambic pentameter. (Using the elevated short u and the slash mark (/), the reader can mark off the unstressed and stressed syllables that occur in pairs five times.) This iambic pentameter follows naturally the English emphasis upon words and syllables as well as the natural rise and fall of English-speaking voices, thus lending reality and sincerity to the message of the poem.