“Sonnet 18” is a sonnet written by famed English playwright and poet William Shakespeare. It is the bard’s most famous and popular lyrical poem and among the more famous poems in English literature. The poem is written in the form of a love confession or a statement of praise about the beloved one’s beauty and charm.

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:

The sonnet consists of fourteen lines in total, which follow an ABAB CDCD EFEF GG rhyme pattern. The lines are of iambic pentameter, which is the most commonly used metric line in old English poetry and drama. The sonnet is most commonly separated into four distinct sections, identifiable by their changing rhyme scheme, and is composed of three quatrains and a couplet.

Sometime too hot the eye of heaven shines,
And often is his gold complexion dimmed;
And every fair from fair sometime declines,
By chance, or nature’s changing course, untrimmed:

An interesting element of the sonnet is the fact that critics and analysts are often confused when it comes to its classification. Some argue that “Sonnet 18” is a part of Shakespeare’s "procreation sonnets" (the first seventeen sonnets), as it has a similar thematic representation of eternity, which is a common theme in the 15th, 16th, and 17th sonnets. Others say that the sonnet, alongside the 19th, acts as a thematic transition from the previous "procreation sonnets" to the next series of sonnets, which explore themes such as the nature of time and its meaning. As such, the sonnet deals with both eternity and its opposite, positioning the progress of time as something of a battle, a combat to be won, and an enemy to be conquered. Indeed, as time presses in on beauty, the speaker rails against time’s inevitable victory, arguing:

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:

Shakespeare wrote a total of 154 sonnets, many of which share the same themes of love, beauty, and eternity. Because of this, “Sonnet 18” is often compared to Petrarchan sonnets. Shakespeare’s sonnets influenced many poets, writers, playwrights, artists, musicians, scenarists, and even sculptors, and continue to do so to this very day. For this reason, the speaker's claims of poetic immortality in the final couplet bear genuine validity:

So long as men can breathe or eyes can see,
So long lives this, and this gives life to thee.