. "In classical music from Western culture, a diesis (/\u02C8da\u026A\u0259s\u026As/ DY-\u0259-sis; \"difference\"; Greek: \u03B4\u03AF\u03B5\u03C3\u03B9\u03C2 \"leak\" or \"escape\") is either an accidental (see sharp), or a very small musical interval, usually defined as the difference between an octave (in the ratio 2:1) and three justly tuned major thirds (tuned in the ratio 5:4), equal to 128:125 or about 41.06 cents."@en . . .