Viewed overall, there are three basic families of intervals: perfect, major/minor, and augmented/diminished. These are related in a special way. Each interval has what is called its inversion. In order to correctly produce an inversion of any interval, the bottom pitch must be raised one octave or the top pitch must be lowered one octave. Notice that the inverted interval has opposite qualities—in other words, when inverted, a major interval gives a minor interval (and vice versa). Similarly, when inverted, an augmented interval gives a diminished interval (and vice versa).
Some simple rules for inversion of intervals follow: