Distance from a point to a plane

In Euclidean space, the distance from a point to a plane is the distance between a given point and its orthogonal projection on the plane, the perpendicular distance to the nearest point on the plane. It can be found starting with a change of variables that moves the origin to coincide with the given point then finding the point on the shifted plane a x + b y + c z = d {\displaystyle ax+by+cz=d} that is closest to the origin.

Source: Wikipedia — Distance from a point to a plane (CC BY-SA 4.0)