Diminished chords can also be written as C diminished, C dim, C° or C°7. A diminished triad has only 3 notes whilst the diminished 7th has four, however you're usually pretty safe playing a diminished 7th chord in place of all diminished chords if you want.
C diminished 7th has these notes: C, Eb, Gb, Bbb (A)
You can also take any of the chord notes to be the root note. So we can also call this chord:
C diminished 7th
Eb diminished 7th
Gb diminished 7th
A diminished 7th
Have a look at our previous diminished chord for some more examples where to use these guitar chords.
C diminished 7th can also be thought of as B7b9.
Tune in tomorrow for another guitar chord of the day!