Parallel lines are those lines that maintain a certain distance from each other, and despite extending their trajectory to infinity, they never meet or touch at any point; In other words, parallel lines are understood to be those that are in the same plane, do not have any common point and show the same slope, that is, they must not touch or cross, not even their extensions cross, a clear example of this are the train tracks. To clarify its significance we must give a brief concept of what a line is; and this is a consecutive series of points, which are all located in the same direction, which are characterized by being continuous and infinite, that is, they have no beginning or end.
Among the properties of a parallel line are: symmetric, if one line is parallel to another, then it will be parallel to the first one; reflective, every line is parallel to itself; corollary, all those parallel lines present the same direction; corollary of the transitive p, two lines parallel to a third will be parallel to each other; and transitive, if a line is parallel to another and at the same time to a third, the first will be parallel to the third line.
An opposite case to parallelism is the relation of perpendicularity between two lines, where at a certain point they are divided, resulting in four residual angles, that is, we speak of four angles of 90 ° each; As an example, we can imagine the intersection of two streets where you can clearly see the four right angles that are formed at each corner.
