What is a sonnet?

The sonnet originated in 13th-century Italy and was perfected by Petrarch, whose sonnets split into an eight-line octave and a six-line sestet. In England, poets developed a form of three four-line quatrains followed by a rhyming couplet, known as the Shakespearean sonnet. William Shakespeare wrote 154 sonnets, published in 1609. Most English sonnets are written in iambic pentameter, lines of ten syllables with alternating unstressed and stressed beats. Later poets from John Milton to Elizabeth Barrett Browning and Pablo Neruda adapted the form in new ways.