Repetition of a sound, syllable, word, phrase, line, stanza, or metrical pattern is a basic unifying device in all poetry. It may reinforce, supplement, or even substitute for meter, the other chief controlling factor in the arrangement of words into poetry. Primitive religious chants from all cultures show repetition developing into cadence and song, with parallelism and repetition still constituting, most frequently as anaphora, an important part in the sophisticated and subtle rhetoric of contemporary liturgies (e.g., the Beatitudes). Frequently also, the exact repetition of words in the same metrical pattern at regular intervals forms a refrain, which serves to set off or divide narrative into segments, as in ballads, or, in Iyric poetry, to indicate shifts or developments of emotion. Such repetitions may serve as commentary, a static point against which the rest of the poem develops, or it may be simply a pleasing sound pattern to fill out a form ("hey downe adowne"). As a unifying device, independent of conventional metrics, repetition is found extensively in free verse, where parallelism (repetition of a grammar pattern) reinforced by the recurrence of actual words and phrases governs the rhythm which helps to distinguish free verse from prose (e.g., Walt Whitman, "I Hear America Singing"; Carl Sandburg, Chicago, The People Yes; Edgar Lee Masters, Spoon River Anthology).
The repetition of similar endings of words or even of identical syllables (rime riche) constitutes rhyme, used generally to bind lines together into larger units or to set up relationships within the same line (internal rhyme). Such repetition, as a tour de force, may be the center of interest in a poem, as Southey's "The Cataract of Lodore" and Belloc's "Tarantella," or may play a large part in establishing the mood of a poem, as in Byron's Don Juan.
Front-rhyme, or alliteration the repetition of initial sounds of accented syllables frequently supplements the use of other unifying devices, although in Old English poetry it formed the basic structure of the line and is still so employed occasionally in modern poetry, as by Gerard Manley Hopkins and in W. H. Auden's The Age of Anxiety. Alliteration also may be carried beyond the limits of a single line and may even operate in elaborate patterns throughout a poem as a counterpoint to other relationships indicated by different sorts of repetition, such as rhyme, metrical pattern, and assonance. The exact repetition of sounds within a line serves as a variety of internal rhyme ("Come here, thou worthy of a world of praise," Chapman, "The Odyssey"). Another repetitional device used chiefly in a decorative or supplemental function rather than in a structural one is assonance, the use of similar vowel sounds with identical consonant clusters. Such a poem as G. M. Hopkins' "The Leaden Echo" will illustrate abundantly how these "supplemental" devices of internal rhyme, alliteration, and assonance may be made into the chief features of the poetic line to support an unconventional system of metrics.
The repetition of a phrase in poetry may have an incantatory effect as in the opening lines of T. S. Eliot's "Ash-Wednesday":
Because I do not hope to turn again
Because I do not hope
Because I do not hope to turn....
The remaining 38 lines of the opening section of the poem might well be studied as an example of the effects of phrasal repetition, containing as they do no less than 11 lines clearly related to the opening 3 and serving as a unifying factor in a poem otherwise very free in structure.
Sometimes the effect of a repeated phrase in a poem will be to emphasize a development or change by means of the contrast in the words following the identical phrases. For example, the shift from the distant to the near, from the less personal to the more personal is emphasized in Coleridge's "Rime of the Ancient Mariner" by such a repetition of phrases:I looked upon the rotting sea,Allusion or quoting is a special case of repetition, since it relies on resources outside of the poem itself for its effect. Here, as with the pun, the effect of the repetition is diffusive rather than unifying, seeming frequently to be an extraneous, if graceful, decoration. Hence, with the exception of a few poets who have used it as a basic technique (T. S. Eliot, The Waste Land; Ezra Pound, Cantos), its chief use has been humorous, as in Robert Frost's "A Masque of Reason" or in W. S. Gilbert's "Bab Ballads."
And drew my eyes away;
I looked upon the rotting deck,
And there the dead men lay.
The repetition of a complete line within a poem may be related to the envelope stanza pattern, may be used regularly at the end of each stanza as a refrain, or in other ways. The multiple recurrence of a line at irregular intervals as in Catullus' 64th Ode, or the line "Cras a met qui numquam amavit, quique amavit cras a met," which occurs ten times in the 92 lines of the Pervigilium Veneris, illustrates the effect of a repetition of a specific line apart from a set place as furnished by stanzaic structure. Rarely a line may be repeated entire and immediately as a means of bringing a poem to a close, an extension of the method of bringing a sequence of terza rima to a close with a couplet:And miles to go before I sleep,
And miles to go before I sleep.
(Frost, "Stopping by Woods on a Snowy Evening")