F Diminished chord (Fdim) on the guitar fretboard

The F Diminished chord (Fdim) is made of F (the root), Ab (minor third) and Cb (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.