The function of rhyme in poetry is to establish structure while creating a pleasant or even beautiful symmetry among a poem’s verses. In the ages before the written word, rhyme also assisted with memorization, a role it still performs today. Not all poems rhyme, and not all rhymes are poetry; rhyme is also employed in songwriting and advertising copy, for example. The use of rhyme in poetry, however, is the most common application of both, learned by most people while they are still children. To many people, in fact, any rhyme is a poem and vice versa.
Rhyming verse is one of the oldest literary forms, predating the establishment of writing itself. There is good reason for this: Many primitive cultures used oral, or spoken, narratives to relay important aspects of their history and culture to younger generations. Rhyme is a powerful mnemonic, or memory aid, so many of these narratives were put in rhyming-verse form by bards and poets. Rhyme continued to be used for this function until relatively recent times, as literacy was not widespread until the 19th and 20th centuries. The more talented poets could use rhyme as an asset rather than a limitation.
William Shakespeare, for example, was expert at using rhyme in poetry and drama alike. In his plays, he would often end an act by having a character speak a rhyming couplet, such as The play’s the thing\Wherein I'll catch the conscience of the King.” In Shakespeare’s time, poets often used complex rhyme schemes. For example, the sonnet, a poetic form often employed by Shakespeare, employs several quatrains, in which four lines share two rhymes, followed by a single set of rhyming lines. Other poetic forms in use at the time, such as the sestina, employ even more complicated rhyme schemes.
Another important function of rhyme in poetry is to create symmetry, a repeated pattern that often conveys a sense of harmony and beauty to an audience. This can be achieved even if the rhyme is imperfect and the words sound similar but not exactly alike, such as “back” and “fact.” This is such an important aspect of poetry that translators of poems in foreign languages will sometimes take pains to ensure their translations rhyme as well as the original. This is often done with Dante’s Divine Comedy, for example, and Chaucer’s Canterbury Tales, written in an early form of English that bears little resemblance to the modern language.
The symmetrical and memory-aiding functions of rhyme in poetry mean that they are often used in other contexts. Verses called nursery rhymes, sometimes containing archaic or nonsensical words and images, are taught to young children to introduce important concepts and because the rhymes are easy for children to remember. Popular songs employ rhyme for the same reasons poems do. Inexpert writers often force their poems to rhyme, even if the verse suffers as a result. Modern poets sometimes dispense with rhyme entirely, preferring non-rhyming formats known as blank verse or free verse.