perpendicular
If two lines intersect at right angles then they are perpendicular!
Two lines that intersect to form right angles are perpendicular.
Perpendicular lines intersect each other at right angles.
They are called perpendicular lines that intersect each other at right angles.
If two lines are not perpendicular then they cannot intersect to form any right angles.
The contrapositive to the statement, "if two lines intersect to form right angles, then they are perpendicular," is "if two lines are not perpendicular, then they do not form right angles."
They are perpendicular
Perpendicular angles.
Two planes intersect at a line
Two lines that intersect and form 90-degree angles (right angles) are "perpendicular" to each other. You would call them "perpendicular lines."
Perpendicular
parallellines