Read william shakespeare’s sonnet 18. note that it is divided into three quatrains followed by a concluding couplet. which two signals indicate the start of the third quatrain in line nine? shall i compare thee to a summer's day? thou art more lovely and more temperate: rough winds do shake the darling buds of may, and summer's lease hath all too short a date: sometime too hot the eye of heaven shines, and often is his gold complexion dimm'd, and every fair from fair sometime declines, by chance, or nature's changing course untrimm'd: but thy eternal summer shall not fade, nor lose possession of that fair thou ow'st, nor shall death brag thou wander'st in his shade, when in eternal lines to time thou grow'st, so long as men can breathe, or eyes can see, so long lives this, and this gives life to thee.

The ninth line of the sonnet brings in a major change of tone. Shakespeare jumps on elaborating the immortality of his lover rather than continuing the criticism of the sun.  Moreover, the limitations of nature are replaced by his lover’s thoughts and he claims that his darling is not bounded by the rules that are being displayed.

In line-4, the summer is stated as ”eternal summer”, since it keeps returning every year. And noticing from the previous personifications employed in the sonnet, we can easily recognize the similarity between “summer’s day” and “thee”. Both can be eternal or can fade with time. This is the major reason why the author takes a turn on line-9, as both of them have only one threat-time; and the third force that can eternalize them both is the poetry that the author has created.

To conclude, we can easily notice the turn in topic and breaking of the stanza.

intonation based on rhythm.