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 Related Terms
 Parallel Lines:  Two lines are parallel if they lie in the same plane and they do not intersect.
Line: One of the basic undefined terms of geometry. A line has no thickness but its length goes on forever in two directions.
Plane: One of the basic undefined terms of geometry. A plane goes on forever in all directions (in two-dimensions) and is "flat" (i.e., it has no thickness).
Intersecting Lines: Two lines that cross each other. Lines intersect at one point unless the lines fall directly on top of each other (in which case they are essentially the same line and are sometimes called coincidental).
Perpendicular Lines: Two lines are perpendicular if they intersect at a right angle.
Point of Intersection: The point at which two or more lines intersect (cross).