A slash chord, or altered bass note chord, is a chord with a bass note other than the root. Slash chords are indicated by using two symbols separated by an oblique stroke. The first symbol represents the chord, and the second symbol represents the bass note. For example, D/C means you should play a D major chord with a C note in the bass.

Inversions can be indicated in the same way. For example, C/E denotes a C major chord in first inversion, and C/G a C major in second inversion.