♭5: Flatted Fifth Scale Degree
1. Flatted Fifth Scale Degree or Flat Five indicates a note in a scale or chord that is one fret (or half step) lower in pitch than the fifth scale degree of the Major scale built on the same root.
2. Can also refer to the interval or musical distance of 6 frets or half-steps. Often called a Tritone (6 frets = 3 whole steps), or a Diminished Fifth, as this interval is found in the Diminished Scale (w/h) and Diminished chord.
3. Can also be called the Blue Note when used in the Blues Scale.