The word straight comes from the Latin "rectus" which means "right"; which is a participle of the verb "regere" which means to rectify, straighten or rule and that this verb also comes from an Indo-European root. The RAE defines straight as an adjective; It does not lean one way or the other, nor does it make angles or curves. The word straight is also given to a part of a dress that is simple cut without pleats, darts etc. The piece or section of road, railway line, road among others, is also called straight. But its most common use is in the geometry that is called a line or straight line to a series or row of points that have or follow the same direction; These lines have neither beginning nor end; that is, it is that line that joins two points in the same plane, by means of an ordered sequence.
The straight line has a certain length or extension; It is also one of the fundamental and basic elements of geometry together with the point and the plane and is named with a lowercase letter. There are several types of lines, including parallel lines, which are those that are located in the same plane that, no matter how long they last, never intersect and do not have any common point, when the points of both are at the same distance, these they can be straight or inclined; then there are the secant lines, they are composed of two straight lines joined by a single point, which makes them cut once; and finally the perpendicular lineswhich are secant lines that divide the plane into four equal parts, forming four right angles.
