Parallel lines

This quick wiki entry explores very briefly what parallel lines are. The word “Parallel” comes from the Greek word para allelois meaning “beside one another”.

Lines are parallel if they lie in the same plane, and are the same distance apart over their entire length. Parallel lines will never meet, no matter how far they are extended. The following are the basic facts about parallel lines.

• Vertically opposite angles are equal.
• Corresponding angles are equal.
• Alternate angles are equal.
• Co-interior angles add up to 180°.

We draw arrows on the lines to show that they are parallel as shown in the figure above.