The poet begins by asking a question: should he compare the beautiful person he is writing about to a warm, sunny summer's day? 'Thee' is an old word for 'you'.

He immediately answers his own question, stating that 'you' (thou art) are even more beautiful and gentle ('temperate') than a summer's day.

Summer days aren't always perfect; sometimes strong, 'rough winds' can damage the delicate, beloved ('darling') flowers that bloom in May.

Summer doesn't last forever; its time ('lease') is too short, and it ends ('hath' means 'has'). The beauty of summer is fleeting.

Sometimes the sun, which he calls 'the eye of heaven', shines too fiercely and can be uncomfortably intense, making a summer's day less pleasant. 'Sometime' means 'sometimes'.

And often, the sun's bright, golden face ('complexion') is hidden or made dull ('dimm'd') by clouds, making the day less bright and glorious.

He explains that everything beautiful ('fair'), whether it's a summer's day or another lovely thing, eventually loses its beauty or fades away ('declines').

This fading happens either by accident, like a sudden storm, or because nature itself naturally changes and removes ('untrimm'd') the beauty it once had.

But the beauty of the person he loves, which is like an endless summer ('thy' means 'your'), will never fade away or diminish.

And 'you' (thou) will not lose the beauty ('fair') that you own or possess ('owest'). Your beauty will remain yours forever.

Death will never be able to boast ('brag') that 'you' (thou) are lost in its shadow, because your beauty will defy its power.

Because 'you' (thou) will live on forever, growing into time itself, preserved in his immortal poetry ('eternal lines'), which will keep your memory alive.

He says that as long as there are people alive in the world who can breathe and whose eyes can see, meaning as long as humanity exists and can read.

So long will this poem live, and this poem will keep 'your' (thee) beauty and memory alive forever, ensuring you are never truly gone.

Sonnet 18 is one of William Shakespeare's most famous poems. Written in the late 16th century, it is part of a series of sonnets addressed to a young man, often called the 'Fair Youth'. In this poem, Shakespeare praises the beauty of his friend, arguing that his poetry will immortalize this beauty, making it last longer than any summer. William Shakespeare (1564-1616) was an English playwright, poet, and actor, widely regarded as the greatest writer in the English language and the world's pre-eminent dramatist. He is often called England's national poet and the 'Bard of Avon'.