Assonance—the repetition of a vowel sound in stressed syllables near enough to affect the ear—has been as important as alliteration. Such vowel echoes have been employed in three chief ways. They have been simply harmonious, as in Swift's “So rotting Celia stroles the street / When sober folks are all in bed,” where the echo of [i] and [o] may be more pleasing to the ear than the two alliterations. Assonance has been used for structural effects and for emphasis: it has bound adjective to noun, from Beowulf's “ēōwralēōde”—a popular formula—to Thomas' title “The White Giant's Thigh”; it has bound the lines of a couplet, as in Spenser's “All in a vele of silke and silver thin / That hid no whit her alablaster skin”; it can emphasize rhythmical stresses, as in Shakespeare's “Do I delight to die, or life desire”; it can emphasize rhetorically balancing words, the names in Butler's “Didst inspire Witers, Prin, and Vickears,” or the verbs in Dr. Johnson's zeugma “No dangers fright him and no labors tire.” Assonance can also be onomatopoeic when it repeats the vowel of a key word, as in Pope's “Now pleasing sleep had seal'deach mortal eye; / Stretch'din their tents the Grecian leaders lie.”