parallel lines are parallel if they are always the same distance apart (called “equidistant”), and will never
Created where a transversal crosses two (usually parallel) lines. Each pair of interior angles are inside the parallel lines, and on the same side of the transversal.
Try this Drag an orange dot at A or B. Notice that the two interior angles shown aresupplementary (add to 180°) if the lines PQ and RS are parallel.