This lesson introduces the undefined terms in geometry, which are the foundational building blocks of all geometric concepts: point, line, and plane. These terms are called undefined because they cannot be precisely defined using simpler terms; instead, they are described based on intuition and physical models. A point indicates a position or location in space. It has no size, length, width, or depth. A line is a straight path that extends infinitely in both directions. It has length but no thickness and is defined by at least two points. A plane is a flat surface that extends infinitely in all directions. It has length and width but no thickness and is defined by at least three non-collinear points. Understanding these undefined terms is crucial for developing further geometric definitions, theorems, and problem-solving skills.

1. (IF YOUR HAPPY IF YOU KNOW)
I. There is a point in the subject geometry.
(2x)
(Clap your hands 3x)
There is a point. (4x)
There is a point in the subject geometry.
(Clap your hands 3x)
II. There is a line in the subject
geometry. (2x)
(Stamp your feet 3x)
There is a line. (4x)
There is a line in the subject geometry.
(Stamp your feet 3x)
III. There is a plane in the subject
geometry. (2x)
(Hooray!)
There is a plane. (4x)
There is a plane in the subject geometry.
(Hooray!)
IV. There is a point. (Clap your hands
3x)
There is a line. (Stamp your feet 3x)
There is a plane. (Hooray!)
In the subject geometry. (3x)

2. LEARNING OBJECTIVES
At the end of the lesson, you should be able to:
define the undefined terms in geometry;
appreciate the representations of points, lines
and plane in real life; and
illustrate and name the points, line and plane.

3. Let's try!
Sesame seed
board
rope
Corner of a box
Edge of a table
notepad
carpet
pencil
Tip of a pen

4. Point, line and plane
Point
Line
Plane

5. UNDEFINED TERMS IN
GEOMETRY
By: Lea Mae B. Sakiwat

6. UNDEFINED TERMS
Terms that can be described but
can’t defined since it is just an idea.
In Geometry, there are three
undefined terms.

7. UNDEFINED TERMS
Point
Line
Plane

8. POINT
 a point has no dimension or actual size.
Thus, it has no length, no width, and no
height (thickness)
A point is usually represented by a small
dot.

9. POINT
A point is usually named with a CAPITAL LETTER.
point A
A
point B point C
B C
point D
D

10. POINT
We can associate point to our real-
life.
Example:
sesame seed corner of a box tip of a pen

11. LINE
A line has infinite length, no
width and no height and it
extends to one dimension only.

12. LINE
A line is named by a single lowercase script
letter, or by any two ( or more) points which
lie on the line.
l or line l
or line AB
A B

13. LINE
Line can also be exhibited to real-life
situation.
Example:
Edge of a table rope pencil

14. PLANE
A flat surface that extends infinitely
along its length and width.
It is like an “infinite sheet of paper”.
It has length and width but no
thickness.

15. PLANE

It is named by a single script CAPITAL LETTER or
by any three points in the plane which are not on the
same line.
L I plane m plane IFE
plane LIF plane ELI
plane FEL
E F
m

16. PLANE
Plane can also be exhibited to real-life
situation.
Example:
board notepad carpet

17. LET’S TRY!
DIRECTIONS: Tell whether each of the following
represents a point, line or a plane.
1. Stars in the sky
2. Curtain rod
3. Cartolina
4. Mole
5.Handkerchief

18. TRY YOURSELF!
DIRECTION: Using the illustration below, determine what is ask:
1. Name all the points.
2. Name all the lines using a script letter.
3.What is the other name for line a
4. Using a script letter, named a plane formed by four lines.
5. Name the plane in three different ways using three points.
a b
W
X
L c
Y d
Z

19. ACTIVITY:
½ CROSSWISE
BY TWO’S
Draw and label the diagram.
1. Line OP
2. plane LOVE
3. plane S
4. line f containing in plane Q
5. point B contained in plane Q
6. line CD on plane B and point E not on the plane

20. THE END!!
Thank you !!