This document provides an overview of basic geometry concepts including: - Points have no dimension and are named using capital letters - A line has no end points, is straight, and goes off to infinity in two directions - A line segment is part of a straight line with two distinct end points - A ray has one endpoint and extends off to infinity in one direction - Lines, line segments, and rays can intersect at a single point - A plane is a flat, two-dimensional surface that can be named using points or a cursive letter

1. Geometry Dots &
Lines
Made by Listening Daisy, based on notes from her Geometry
Class (with permission from her instructor).

2. Table of Contents
• Slide 3: What is a Point?
• Slide 4: Mini Lesson: What Letters Not To Use When Naming Points
• Slide 5: What Is A Line?
• Slide 6: How To Name A Line
• Slide 7: What Is A Line Segment?
• Slide 8: What Is A Ray?
• Slide 9: Name That Ray!
• Slide 11: Mini Lesson: Additional Way to Name A Line
• Slide 12: What Is Collinear?
• Slide 13: What Is A Plane?
• Slide 14: What Is Intersection?
• Slide 16: Mini Lesson: Lines & Intersection
• Slide 17: What Is Space?

3. What is a Point?
• Points have no dimension they are “a place in space”.
• When you name a point, use capital letters (usually
the Roman Alphabet is used, but sometimes Greek
letters are used).
A

4. Mini Lesson: What Letters Not
To Use When Naming Points
When naming points, try not to use letters like T and S due
to the fact they could be easily confused with something
else.
For example, S and 5 look very similar.

5. What Is A Line?
B
A
AB
Symbol for the line:
• It has no end points
• It has an infinite number of points
• It is straight and not curved
• Lines go off towards infinity in two directions

6. How To Name A Line
• Now I’m sure you saw the symbol on the top right corner of
the slide before this. is the abbreviation for a line, it is the
name of the line. To make this symbol there must be at least
two points on a line. Let’s use the line below as an example.
• Since it has over two points, we can name it. You can only use
two letters in the name however.
• It is preferred that the letters of the name are read left to right
as in the names AB, BC, & AC. It is also possible to use names
like BA, CB & CA though.
AB
B
A C

7. What Is A Line Segment?
• Straight
• Made up of points
• To name it, you use the end points, not the points on the
line.
A B
AB
Symbol for the line:

8. What Is A Ray?
• Ray: half a line, on one end it has a finite end point and on the
other end it goes off infinitely
• Straight
• Needs two points to name: when naming, always start with
the end point. It can’t be BA because BA is:
A B
AB
Symbol for the line:
B
A

9. Name That Ray!
Where are the rays?
A B C

10. Name That Ray!
A B C
The rays that are located here are BA, BC & AC
A B
B C
A C

11. Mini Lesson: Additional Way to
Name A Line
• An additional way to name a line is to use a lower case
cursive letter.

12. What is Collinear?
• When there are more then three points on the same line.
• Ex 1: A, B & C are collinear
• Ex 2: A, B & C are not collinear
A B C
A B C

13. What Is A Plane?
• Flat
• 2-dimensional
• Named using its four points or a single cursive letter.
or
A B
C D
Note: The cursive letters must always be capitalized

14. What Is Intersection?
• When lines cross, it’s in the form of a point
• When planes cross it’s a line segment
• When a line crosses a plane it’s a point.

15. What Is Intersection?
• When three planes intersect, it’s a point.

16. Mini Lesson: Lines &
Intersection
• A line can only intersect at one point.
• For example, due to the fact that the line is straight, it cannot
curve to create another point inside the shape.

17. What Is Space?
• A set of all possible points