Repetition is a common component of poetry and may appear as a single word or phrase used throughout a poem or as an entire stanza reused repeatedly. Different poets have used repetition in poetry to achieve many different ends, ranging from emphasizing a particular point to making a poem easier to memorize. It is often used to supplement or even replace some formal components of poetry, such as meter and rhyme, as well. Repetition may also refer to the repetition of specific sounds to produce particular effects, such as alliteration or rhyme. Many poets focus on the sound and rhythm of their poems at least as much as on the meanings, so repetition is a powerful tool because it can be used to manipulate both.
One of the most common uses of repetition in poetry is emphasizing a particular word or phrase for purposes such as drawing attention to a particular theme or pointing out contrasting uses of a given word. The degree to which repetition is used varies widely. Some poems repeat the same word or phrase in every single line while others repeat it only in a few stanzas or only twice in the entire poem. Repetition can even transcend the bounds of a single poem. Poets often release books of their poetry, and repetition may be used throughout their poems to give a sense of unity and cohesion to the collection.
On a smaller scale, repetition can refer to the repetition of particular sounds. Repeated sounds are used to produce rhymes, which are very common in many different forms of poetry. Some poets choose to favor a certain subset of sounds through an entire poem to create or to avoid a certain effect, often so that form matches meaning. Repetition in poetry about love and comfort, for instance, may involve favoring soft, gentle sounds while avoiding harder or harsher sounds, such as those produced by a hard "k" or "g."
Before physically writing poetry became a widespread practice, important poems were often passed down through oral tradition. Repetition made such poems far easier to memorize, as repeated segments could be used to measure progress through the poem and were, in themselves, easy to memorize. Many early epics and other long poems in particular are characterized by the presence of repeating sections. Repetition in poetry of this form often serves the double purpose of making memorization easier and adding emphasis to important points.