When there is no common point between two straight lines on a plane, two planes in space and a straight line in space and a plane, they are said to be parallel. Parallel lines will not intersect at any distance.
Parallel nature:
1. Two parallel lines are cut by a third straight line and are complementary to the lateral inner angle (hereinafter referred to as "the two straight lines are parallel and complementary to the lateral inner angle").
2. Two parallel lines are cut by a third straight line, and their internal dislocation angles are equal (referred to as "the internal dislocation angles of the two parallel lines are equal").
3. Two parallel lines are cut by a third straight line, and their isosceles angles are equal (referred to as "two parallel lines with equal isosceles angles").
4. There is only one straight line parallel to this straight line at a point outside the straight line (parallel axiom).
5. If two straight lines are parallel to another straight line, they are also parallel to each other.
6. The distance between parallel lines is equal everywhere.