A semitone is the distance between a node and its nearest one on a keyboard. It can also be named as half step. Here we know the pitch is the difference between two notes. So semitones can be explained in terms of pitch. Semitones are called the smallest interval in western music. In a 12-note approximately equally divided scale, any interval can be defined in terms of an appropriate number of semitones. They are a whole tone or major second is 2 semitones wide, a major third 4 semitones, and a perfect circle of fifth 7 semitones. The whole tone is just twice the size of a half-step/ semitone.