A unit of measure of the width of a
musical interval, equal to 1/100 of a
semitone,
not a
whole tone. You can find the number of cents in a
just intonation interval from the
frequency ratio by this formula:
cents = log(ratio) / log(2) * 1200
Thus the octave, ratio 2/1, measures 1200 cents, which makes sense because it is equal to twelve equal tempered semitones each 100 cents.