B Diminished chord (Bdim) on the guitar fretboard

The B Diminished chord (Bdim) is made of B (the root), D (minor third) and F (diminished fifth). The fretboard shows every one of them across the neck in standard tuning (E A D G B E), and plays them back so you can hear the chord.

The diminished triad stacks two minor thirds, giving a root, a minor third and a flat five. It is a compact, symmetrical shape that tends to repeat at regular distances on the neck. Add a seventh and it becomes the diminished seventh or the half diminished chord.