Oblique Lines

Two intersecting lines are called oblique lines if they divide the plane into two pairs of congruent opposite angles that are not 90°.

In other words, two lines are oblique if:

• They intersect
  They share exactly one point.
• They are not perpendicular
  They do not form four 90° angles.

Conversely, when two intersecting lines divide the plane into four congruent 90° angles, they are called perpendicular lines.

And so forth.