What are two lines called when they intersect to form a right angle?

When two lines intersect to form a right angle, they are referred to as perpendicular lines. This occurs when the angle between the two lines measures exactly 90 degrees. The defining characteristic of perpendicular lines is this right angle, which signifies that they are not only crossing each other but doing so at specific orientations that divide the angle into two equal parts of 45 degrees.

Understanding that perpendicular lines are significant in various geometric constructions helps to reinforce concepts such as constructing squares or rectangles, where right angles are essential. This terminology is distinctly different from other types of lines, such as parallel lines, which never intersect, and skew lines, which do not lie in the same plane and cannot intersect at all. Intersecting lines, while they do cross each other, do not necessarily form right angles, as they can create angles of varying measures. Hence, the term that specifically indicates the presence of a right angle at the intersection is "perpendicular lines."