In music or music theory, a thirteenth is the interval between the sixth and first scale degrees when the sixth is transposed up an octave, creating a compound sixth, or thirteenth.
A thirteenth chord is the stacking of six (major or minor) thirds, the last being above the 11th of an eleventh chord. Thus a thirteenth chord is a tertian (built from thirds) chord containing the interval of a thirteenth, and is an extended chord if it includes the ninth and/or the eleventh. The jazzy thirteenth is a very versatile chord and is used in many genres. Since 13th chords tend to become unclear or confused with other chords when inverted, they are generally found in root position.