The most basic of all poetic sound devices, rhyme makes two or more lines sound pleasing because they end with the same syllable. For example, "stood" and "could" both end with the sound "-ood." Consider these lines from Robert Frost's poem "The Road Not Taken":
"And be one traveler, long I stood
And looked down one as far as I could"
Because the two lines end with the same sound, they rhyme.
Not all poetry rhymes; great poets such as T.S. Eliot, Shakespeare and E. E. Cummings often wrote in free verse or blank verse, which don't use rhyme.
Although less obvious than rhyme, meter forms an essential backbone for traditional poetry. Meter organizes the syllables in each line so that the accents or emphases fall in the same place in every line. For example, consider Ogden Nash's short poem "The Cow":
"The cow is of the bovine ilk;
One end is moo, the other, milk."
The first line follows a pattern of one unaccented syllable and then one accented syllable: "the COW is OF the BOvine ILK." The second line follows the same pattern; "one END is MOO ... " Hence, because both lines follow the same pattern of accents, the poem is metered.
Some poems contain refrains, which means they repeat words or phrases multiple times. Edgar Allen Poe's "The Raven," for example, repeats the phrase "nevermore" in the last line of 11 stanzas. One stanza ends with "Quoth the raven, 'Nevermore'"; another stanza ends with "Then the bird said, 'Nevermore.'" By repeating the word "nevermore," Poe emphasizes the misery of the poem's narrator because he can never reclaim the past.
An onomatopoeic word sounds like its meaning. For example, when you say the word "fizz" aloud, it sounds like a fizz; the long "z" sound mimics the sound of fizzing. "Boom," "clunk" and "bubble" similarly mimic the sounds of the things they communicate.
Other onomatopoeic words mimic sounds more directly, such as the words used to describe animal noises, like "moo" and "baa."
Similar to rhyme, assonance, consonance and alliteration repeat identical sounds. Unlike rhyme, however, they don't repeat an entire ending sound; instead, they each repeat a different part of the word.
Assonance repeats the same vowel sound, but not the same consonants. For example, "dog," "mock" and "strong" each contain a short "o" sound, even though they begin and end with different consonants.
Consonance reverses the pattern, repeating ending consonants but not vowels; for example, "tiff," "off" and "rough" each ends with the "f" sound, even though their vowels make different sounds.
Alliteration repeats beginning consonants, but not middle vowels or end consonants. For example, "glitter," "glum" and "glue" all begin with "gl," but they end differently.