Answer:
Poetry, like other kinds of artistic expression, comes in a variety of shapes and sizes. The sonnet, which originated in the thirteenth century and is still used today, is a poetic form to which writers as varied as John Donne, Robert Frost. There are reasons the form has been around for so long. For both writers and readers, the sonnet offers advantages, including its versatility, its place within a long poetic tradition, and the way it lends itself to a concentrated focus and the rigorous use of language.
Rigorous Language
One advantage of a sonnet, or of any poem in which form, rhythm and rhyme are strictly defined, is that it forces the poet to work within very specific parameters, which results in an increase of poetic discipline. Whereas free verse allows a poet to follow his whimsy to a large extent, the demands of the sonnet form require every word to be carefully weighed, leading to potentially more satisfying poetry, as the poet is forced to become more intentional and careful with the words he chooses.
Concentrated Focus
The sonnet may be the perfect poetic form for the expression or elaboration of a single thought or feeling. With its relatively short length -- just fourteen lines, usually in iambic pentameter -- the sonnet provides the perfect laboratory for a poet's exploration of an intense emotion. Short enough to be manageable to writer and reader alike, the sonnet is nevertheless long enough to do justice to complex poetic subjects.
Versatility
Another reason the sonnet is so popular among poets is that it has shown a great ability to adapt to different needs and purposes. Sonnets lend themselves to many subjects and themes, such as love, politics, nature, death -- the possibilities are endless. Even the sonnet’s meter and rhyme, which in some ways define the form, have proven to be fair game for poets who favor innovation and experimentation. For instance, George Starbuck's poem "Sonnet in the Shape of a Potted Christmas Tree," while having more than fourteen lines, roughly follows a sonnet's traditional rhyme scheme.
A Long Tradition
The sonnet has endured the test of time. From the earliest sonnets of 14th-century Italy to sonnets written today, every sonnet is a part of this great tradition. Whether obediently following the rules for rhythm and rhyme scheme or flouting those rules to break new ground and shake things up, every sonneteer has to, in some measure, reckon with the poets who have come before him. Shakespeare's famous Sonnet 130, for example, plays on and against the tradition of love sonnets that idealize the women they take as their subjects. Like all traditions, the demands of the sonnet can be both limiting and liberating, but they can never be ignored.
