A sonnet is a special form of poetry that takes its name from the Italian word sonetto, which means “little song” or “little sound.” Although English poet William Shakespeare is famous for his plays, he also wrote 154 sonnets (not including the ones that appear within his plays).

Sonnets are lyrical poems of 14 lines that follow a specific rhyming pattern. Sonnets usually feature two contrasting characters, events, beliefs or emotions. Poets use the sonnet form to examine the tension that exists between the two elements.

Several variations of sonnet structure have evolved over the years. The most common — and the simplest — type is known as the English or Shakespearean sonnet.

Shakespearean sonnets contain 14 lines, which each have 10 syllables and are written in iambic pentameter. Iambic pentameter is a pattern in which an unstressed syllable is followed by a stressed syllable repeated five times.

The da-DUM sound of the human heartbeat is sometimes used as an example of iambic pentameter: da-DUM, da-DUM, da-DUM, da-DUM, da-DUM. The opening line of Shakespeare’s “Sonnet 12″ provides a good example of the da-DUM rhythm of iambic pentameter: When I do count the clock that tells the time…

Shakespearean sonnets follow a specific rhyme pattern — a-b-a-b / c-d-c-d / e-f-e-f / g-g — and the last two lines form a rhyming couplet. Shakespeare’s “Sonnet 18″ — sometimes called “Shall I compare thee to a summer’s day?” — is one of his most famous sonnets:

a          Shall I compare thee to a summer’s day? b          Thou art more lovely and more temperate.
a          Rough winds do shake the darling buds of May,
b          And summer’s lease hath all too short a date.
c          Sometime too hot the eye of heaven shines,
d          And often is his gold complexion dimmed;
c          And every fair from fair sometime declines,
d          By chance, or nature’s changing course, untrimmed;
e          But thy eternal summer shall not fade,
f           Nor lose possession of that fair thou owest,
e          Nor shall death brag thou wanderest in his shade,
f           When in eternal lines to time thou growest.
g          So long as men can breathe or eyes can see,
g          So long lives this, and this gives life to thee.

Another key element of the sonnet is the volta — or “turn” — which is the point in the sonnet where there’s a change from one rhyme pattern to another that signals a change in subject matter. In the example above, the volta occurs in the ninth line when the word “But” signals a subject change and the rhyme pattern changes to e-f-e-f.

In addition to the English or Shakespearean sonnet, two other popular types of sonnets are the Spenserian sonnet (named after poet Edmund Spenser) and the Italian or Petrarchan sonnet. These types of sonnets can be identified by their unique rhyming patterns. There are also more obscure types of sonnets, some of which have no recognizable rhyming pattern.

Over the years, many poets and writers have written sonnets. Some of the more famous sonnet authors include John Donne, John Milton, Ezra Pound, Elizabeth Barrett Browning and Edna St. Vincent Millay.