A semitone is the smallest musical interval commonly used in Western music. It represents the distance between two adjacent keys on a piano keyboard, whether they are white or black. For example, moving from C to C# or from E to F covers one semitone. In terms of pitch, a semitone is the interval that separates two notes that are one half-step apart. This interval is fundamental in constructing scales, chords, and melodies, making it essential for musicians and composers in various genres, including classical, jazz, and pop music.