The letters "c," "a," and "b" are the first three letters of the English alphabet. Each letter has its own unique sound and can represent different phonetic values in various words. For example, "c" can sound like /k/ in cat or /s/ in city. In addition to their phonetic roles, "c," "a," and "b" are also used in various fields such as mathematics and music. In music, "C," "A," and "B" represent specific notes on a scale. In mathematics, they can denote variables or constants in equations.