D-E-F refers to the three letters in the English alphabet that follow C and precede G. Each letter has its own distinct sound and is used in various words and contexts. For example, D can represent a voiced dental stop, while E is a vowel sound, and F is a voiceless labiodental fricative. In addition to their phonetic roles, D, E, and F are also used in various systems, such as grading scales, musical notes, and programming languages. In music, D is the second note in the C major scale, E is the third, and F is the fourth, each contributing to the overall harmony.