A rhyme occurs when two words share similar sounds at the end, usually after the words' last stressed syllables. For example, "advise" and "replies" rhyme, as do "invitation" and "vacation." The most common type of rhyme in English poetry is the masculine rhyme, where the rhyming words end in stressed syllables. An example of masculine rhyme are the words "produced" and "reduced." Conversely with feminine rhyme the final, rhyming syllables are unstressed as in the case of "chances" and "romances." Though poets traditionally use masculine rhymes, Ambrose Bierce uses almost all feminine external rhyme in his poem "The Day of Wrath."
Rhyme is a type of consonance, the resemblance of sound between two words. Sometimes only the ending consonants sound the same, as in "soul" and "all." Usually called "slant rhyme," but also known as "half rhyme" and "off rhyme," this occurs at the external position of a line of poetry. "Alliteration" refers to similar consonant sounds occurring close together in a phrase or line. An example from Dylan Thomas's "Lie Still, Sleep Becalmed" reads, "We saw the sea sound sing, we heard the salt sheet tell." The recurring "s" sound creates a pattern of alliteration. Assonance occurs when vowel sounds within the word repeat, but the consonants do not, as with "ridges" and "wind."
External rhyme, also called "end rhyme," happens at the end of a line and is common in poetry. An example comes from "Stopping by Woods on a Snowy Evening" by Robert Frost: "Whose woods these are I think I know/ His house is in the village, though." Conversely, it is less common for the initial words in poetic lines to rhyme, but this is the case to "To Daffodils" by Robert Herrick: "As yet the early-rising sun/ Has not attained his noon." When two words within a single line of poetry rhyme, this is called an internal rhyme.
Rhyme scheme depends exclusively upon external rhyming, whether masculine, feminine or slant rhyme. In poetic analysis, the rhymes are labeled with a letter of the alphabet, with rhyming words receiving the same letter. In Robert Frost's poem above, "know" and "though" would receive the same letter because they rhyme. In some cases, a poet chooses to employ only one rhyme in a stanza, as in the case of William Blake's "Silent, Silent Night," which is called a monorhyme. Rhyme schemes give poetry structure, and external rhymes serve as a unifying pattern drawing ideas in the poem together.