Triads: The B Diminished Triad - Component Intervals of Diminished Triads, Pt. 1

The long-key third above B is the minor 3rd B-D.

The long-key triad whose root is B is spelled B-D-F.

B-D is a m3, D-F is also a m3.

B-D-F is a diminished triad: the root to third is a m3, as is the third to the fifth.

No other long-key triad is diminished, only B-D-F.