Intonation concerns the fine points of how a scale is tuned. The 12-tone chromatic scale used in Western music is tuned according to the system of equal temperament. In this system the octave is divided up into 12 mathematically equal semitones. The reality of tuning is that this represents only one option and represents a compromise to what is actually possible. Another kind of tuning is called just intonation. This favors pure intervals as defined by their ratios—in other words, perfect fifths of 3/2, major thirds of 5/4, major sixths of 5/3, and so on.