The millioctave (moct) is a unit of measurement for musical intervals.
The millioctave was introduced by the German physicist Arthur von Oettingen in his book Das duale Harmoniesystem (1913).
The invention goes back to John Herschel, who proposed a division of the octave into 1000 parts, which was published (with appropriate credit to Herschel) in George Biddell Airy's book on musical acoustics.
[1] Compared to the cent, the millioctave has not been as popular because it is not aligned with just intervals.
It is however occasionally used by authors who wish to avoid the close association between the cent and twelve-tone equal temperament.