What is a sonnet?

The most famous writer of sonnets is William Shakespeare.  Shakespearean sonnets (and all English sonnets) have three verses of four lines each (called quatrains) with a two-line verse to conclude (called a couplet).  They are typically in iambic pentameter (which means they have a rhythm to them, such as five groups of two beats each), and the rhyme scheme goes abab cdcd efef gg (this means the first and the third line rhyme, the second and the fourth, the fifth and the seventh, etc).

Although every sonnet comes close to following similar patterns, poets can vary them from time to time and still be close enough to the form that the poems fall under the sonnet category (and the vast majority have 14 lines with 10 beats per line).  The other basic sonnet style is called Petrarchan, and it’s the Italian sonnet.  Also 14 lines, of course, it varies in that the first eight lines follow this rhyme scheme:  abbaabba; while the following six are either cdecde or cdcdcd.  Even though most people probably know about sonnets because of Shakespeare, it was actually Petrarch who first established the sonnet form.  Poets in the centuries since have enjoyed making it their own in various ways, and many of the classic poets have at least one sonnet in their repertoire.