The repetition of Letters in a sentence is called?

The repetition of letters in a sentence or word is called alliteration. Alliteration is a literary device in which the same consonant sound is repeated two or more times in close succession. It is often used to create a pleasing sound effect or to emphasize a particular word or phrase. For example, "Peter Piper picked a peck of pickled peppers" and "Betty Botter bought some butter, but the butter Betty bought was bitter".