|Definition:|| qualifies in a Euclidean space: |
- a straight line with respect to another straight line when their associated vectors are orthogonal;
- a straight line with respect to a plane when the line is perpendicular to any line of the plane;
- a plane with respect to another plane when it contains a straight line which is perpendicular to any line of the other plane
Note 1 to entry: Usual wordings for lines are "line A is perpendicular to line B", or "lines A and B are perpendicular", or " A and B are perpendicular lines". Similar wordings are used for the other cases.