Iambic pentameter is a form of rhythm that appears in poetry, songs, and some prose compositions. It is most closely associated with poetry, especially English poetry, which lends itself very well to this particular form of rhythm. One of the most notable writers who worked in the form was William Shakespeare, who was fond of it for both his sonnets and his plays, in which characters classically spoke in verse.
In the poetry world, rhythm is also referred to as “meter.” The meter of a poem is determined by the “feet,” or the syllable patterns in the work. In the case of iambic pentameter, each verse in the poem has five feet, which take the form of iambs, creating a very distinctive meter. The rise and fall of stress in the verse gives it a very melodic feel, and incidentally makes it easier to remember, because people can use the meter as a framework for memorization and recital of poetry.
Iambs are pairs of syllables that can be short and long, or unstressed and stressed. When spoken aloud, an iamb follows a “ba-DUM” pattern, with the first syllable being short or unstressed and the second syllable being long or stressed. In this rhythm, there are five iambs in each line, creating a “ba-DUM ba-DUM ba-DUM ba-DUM ba-DUM” sound which is very regular and rhythmic. The verses may also be designed to rhyme with each other, using a variety of rhyming schemes ranging from creating rhyming couplets to complex interconnected rhymes which unfold over the course of the composition.
Many forms of meter use iambs, because they are easy and natural to say. When poets compose new work, they typically think about the way that syllables will sound together, looking for words that harmonize and create the iambic pattern, whether they are working in iambic pentameter or another form of meter. If the syllables clash with each other, they can make the piece feel stiff, stilted, or unsettling, which can be undesirable unless it is a deliberate effect that is designed to evoke specific emotions in the reader or listener.
The use of various forms of meter in poetic and staged composition is very old. As discussed above, work tends to be easier to memorize and recite when it has a specific meter, which was useful in an era when few things were committed to paper, as people could pass down works of art and traditional stories in metered verse. Metered work also tends to sound more pleasant to the ear, and many poets and authors enjoy playing with meter in their work.