Rhyme scheme is the repetition of rhyming words throughout a poem. It is determined by assigning each unique rhyming line a letter. For example, the rhyme scheme of a poem with alternating rhymes is ABABAB. The rhyme scheme in Edgar Allan Poe’s "The Raven" is significant because the poem has a unique pattern of end rhymes and internal rhymes, creating the atmosphere and the tension in the poem.
End rhyme consists of the rhyming words at the end of each line. In each stanza in "The Raven," the end rhymes of the first and third lines alternate, while the second, fourth, fifth and sixth lines are always "B." For example, the rhyme scheme in the first stanza in "The Raven" is ABCBBB. The repetition of the "B" rhyme throughout the entire poem -- e.g., "Lenore," "door," "lore" -- is what gives the poem its eerie tone and atmosphere.
In each stanza, the first and third lines -- which may seem to have no rhyming partners nearby -- have internal rhymes, meaning the rhyme is located within the line instead of at the end. For example, in line 1 "dreary" rhymes with "weary," and in line 3 "napping" rhymes with "tapping": "Once upon a midnight dreary, while I pondered, weak and weary,/ … /While I nodded, nearly napping, suddenly there came a tapping." The internal rhymes jump out at the listener/reader and create tension in each stanza.