In
music theory, the
tritone is strictly defined as a
musical interval composed of three adjacent
whole tones. For instance, the interval from F up to the B above it (in short, F–B) is a tritone as it can be decomposed into the three adjacent whole tones F–G, G–A, and A–B. According to this definition, within a
diatonic scale there is only one tritone for each
octave. For instance, the above-mentioned interval F–B is the only tritone formed from the notes of the
C major scale. A tritone is also commonly defined as an interval spanning six
semitones. According to this definition, a diatonic scale contains two tritones for each octave. For instance, the above-mentioned C major scale contains the tritones F–B (from F to the B above it, also called
augmented fourth) and B–F (from B to the F above it, also called
diminished fifth,
semidiapente, or
semitritonus).