Assonance is a literary device characterized by the repetition of vowel sounds within closely placed words, creating a musical quality and enhancing the rhythm of a piece. Unlike rhyme, which focuses on the ending sounds of words, assonance emphasizes internal vowel sounds, contributing to the overall mood and tone of the text. It is commonly used in poetry and prose to create emphasis and cohesion. An example of assonance can be found in the phrase "Hear the mellow wedding bells."