2.1 Points, Curves, Lines, Rays and Segments
Points
In geometry, a point is an important concept. A point has a determined place and is symbolized by an x or a dot. A point has no length. 

Geometric figures, lines, planes, spheres, etc can be understood as a construction of an infinite amount of points.
Curves
A curve can be bent or straight, finite and limited by one or two points or infinite and infinitely long.



Infinite right angled curve

Lines
A line is a type of curve which is straight and infinite in both directions. A line can be named with the letter l.
Two lines are parallel if they keep the same distance from each other and never intersect each other (meet) no matter how far they are drawn. Two lines can be written as l_{1} and l_{2}.
Two intersecting lines are two lines which cross each other at one point. The point where the lines meet is called the intersection point.
Ray
A ray is a part of a line. It has an end point and continues on infinitely in one direction.
Segment
A segment is a part of a line which has two end points. You can measure a segments length. We call the end points A and B.
