The repetition of the same vowel sounds in a line is

The repetition of the same vowel sounds in a line is called "assonance." This literary device involves the repetition of vowel sounds in nearby words, but the consonant sounds may be different. Assonance is often used in poetry to create a musical effect or to emphasize certain words or ideas. For example, in the sentence "The rain in Spain stays mainly in the plain," the repetition of the long "a" sound in "rain," "Spain," and "plain" is an example of assonance.