Inversion

Inversion appears in symmetry operations.

The inversion operation takes the point (2,3) and returns (-2,-3).

In 3D inversion takes (4,5,6) and returns (-4,-5,-6).

Mathematically, this is taking all the values and returning all their negatives.

Physically this is going from the point to the origin and then continuing on and the same direction the same length the distance is that it was between where you started and the origin.