1. Introduction to Geometry

2. Ray
A ray is a line with a start point but no end point (it goes to infinity).
Written as AB
Which means Ray AB A B
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3. Can you find the ray?

4. Where’s the ray in this picture?

5. Line In geometry a line: is straight (no curves),B
In geometry a line:
is straight (no curves),
has no thickness, and
extends in both directions (infinitely).
Has no ends A
Written as AB
Which means Line AB
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6. If it does have ends it is called a "Line Segment".
Part of a line connecting two points.
It has definite end points.
The word "segment" is important, because a line extends in both directions without end.
If it does have ends it is called a "Line Segment".
Written as AB
Which means Line Segment AB

7. Endpoint Also just known as a “point.” The ends of a line segment.
One side of a ray.
Does not continue. (means to stop)
endpoint
endpoint

8. Intersecting Lines
Lines that have one and only one point in common are known as intersecting lines.
A minimum of two lines are required for intersection.
The common point where all the intersecting lines meet is called the Point of Intersection.
Also known as Perpendicular Lines
In the figure, there are two lines AB and CD which intersect each other at O.

9. Parallel Lines
Lines are parallel if they are always the same distance apart (called "equidistant"), and will never meet. Just remember:
Always the same distance apart and never touching.
Ex: parallel parking
The red line is parallel to the purple line in both of these cases:
                      
       Parallel lines also point in the same direction.
Example 1
Example 2