semitone

noun4

1. •
   One of two parts, equal or unequal, in which a whole tone is divided.
2. •
   The semitone in 12-tone equal temperament, with frequency ratio of the twelfth root of two.
3. •
   An interval equal to an augmented unison or a minor second, depending on the context and tuning system used.
4. •
   Any of the pitches of a chromatic scale.