Perpendicularity is measured by the degree to which the angle between the x-x AND y-y axis approaches a right angle.

The permissible perpendicular variation of relationship between the bearing surface or the top surface and the axis of the thread (A.k.a. runout or TIR).

(adj.) An orientation control for geometric dimensioning and tolerancing. Perpendicularity is the condition of a surface, center plane, or axis that is at a right angle to a datum plane or datum axis, respectively.

The condition that results when a surface, axis, or centerplane is exactly 90° to a datum.

used in GD&T, perpendiculatiry refers to the condition of a surface, line, or axis, which is orthogonal to a datum plane or axis

Dimensional relationship of a part or datum located at right angles (90º) to a given feature.