In geometry, the perpendicular distance between two objects is the distance from one to the other, measured along a line that is perpendicular to one or both. In particular, see:
Distance from a point to a line, for the perpendicular distance from a point to a line in two-dimensional spacePoint on plane closest to origin, for the perpendicular distance from the origin to a plane in three-dimensional spacePlane (geometry)#Distance from a point to a plane, for the perpendicular distance from an arbitrary point to a plane in three-dimensional spaceSkew lines#Distance, for the perpendicular distance between two lines in three-dimensional spaceDeming regression and total least squares, statistical methods for fitting a line to a data set that use perpendicular distance to measure the quality of a fit