In musical theory an inversion is to write one or more notes of a chord an octave above its position in root form.
For example, the root position of a triad of C major is:
The first inversion means to shift the bottom note (the C) an octave higher:
The second inversion is to write the E an octave above:
The third inversion of a triad cannot be constructed, since shifting the G an octave higher would simply form the original root triad up an octave:
It is, however, possible to find the third inversion of chords which have four notes or more, such as the dominant seventh[?].
In musical counterpoint, inversion refers to a melody turned upside-down.
A Temperature inversion is a meteorological phenomenon where warm air gets trapped above cold, preventing air circulation. When inversions occur, air quality suffers.