This document defines and explains basic geometric figures including points, lines, line segments, rays, planes, and angles. It provides descriptions of each figure and conventions for naming them properly. Examples are given to illustrate the definitions and naming. The document serves as an introduction to the fundamental concepts and terminology of geometry.

1. g e o m e t r i c
f i g u r e s

2. B A S I C
G E O M E T R I C
F I G U R E S

3. UNDEFINEDTERMS
In geometry, some words like point, line, and plane are undefined. Undefined terms are the basic ideas that you can use to build
the definitions of all other figures in geometry. Although you can’t define undefined terms, it is important to have a general
description of their meanings. These terms are essentially the “building blocks” of geometry. Every definition in geometry will
build from the 3 undefined terms: point, line, and plane.
POIN
T
A point indicates a
location and has no
size.
How to Name It:
Named with a capital
letter.
Example:
Point 𝑃
LINE
A line is represented by
a straight path that
extends in two
opposite directions
without end and has no
thickness.
How to Name It:
1. Named using any two
points on the line, in any
order, with a line symbol
(↔) drawn above.
OR
2. Named using a lowercase
letter.
Example:
𝐴𝐵
𝐵𝐴
Line 𝑚
PLAN
E
A plane is represented
by a flat surface that
extends without end
and has no thickness.
A plane contains
infinitely many lines.
How to Name It:
1. Named using any three
points in the plane that
are not on the same line,
in any order.
OR
2. Named using a cursive
capital letter.
Example:
Plane 𝐹𝐺𝐻
Plane 𝐹𝐻𝐺
Plane 𝐺𝐹𝐻
Plane 𝐺𝐻𝐹
Plane 𝐻𝐺𝐹
Plane 𝐻𝐹𝐺
Plane 𝒬

4. A line segment
is part of a line
that consists of
two endpoints
and all points
between them.
A ray is part of a
line that consists
of one endpoint
and all the
points of the
line on one side
of the endpoint.
LINE
SEGMENT
RAY How to Name It:
Named using the two
endpoints, in any
order, with a segment
symbol (−) drawn
above.
How to Name It:
Named using the
endpoint and one
other point, with a
ray symbol (→) drawn
above; the endpoint
is ALWAYS listed first.
Example:
𝑆𝑇
𝑇𝑆
Example:
𝑀𝑁

5. EXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLES
EXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLES
EXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLES
For P1-P4, identify each geometric figure, then give all possible names for the figure.P1: P2: P3: P4:
P5: Is 𝑆𝑅 a possible name for the figure at the right? Explain. P6: Caleb says that the figure below can be named 𝐾𝐽 .Jen says the figure below can be named 𝐽𝐿 .Who is correct? Explain. P7: How many rays are contained in the figure? Name them.

6. EXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLES
EXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLES
EXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLES
For P1-P4, identify each geometric figure, then give all possible names for the figure.
P1:
SEGMENT
𝑄𝑃
𝑃𝑄
PLANE
Plane
𝐵𝐺𝑇
Plane
𝐵𝑇𝐺
Plane
𝐺𝑇𝐵
Plane
𝐺𝐵𝑇
P2: P3: P4:
POINT
Point 𝐷
LINE
𝑁𝐶
𝐶𝑁
Plane 𝑇𝐺𝐵
Plane 𝑇𝐵𝐺
Plane ℳ
P5:
Is 𝑆𝑅 a possible
name for the
figure at the
right?
Explain.
No, the figure is a
ray with endpoint
𝑅. The endpoint
must come first
when naming a ray
so the correct name
is 𝑅𝑆.
P6:
Caleb says that the figure
below can be named 𝐾𝐽 .Jen
says the figure below can be
named 𝐽𝐿 .Who is correct?
Explain.
They are both correct
because points 𝐾, 𝐽, and 𝐿
are all points on the line,
and a line can be named
with any two points on the
line.
P7:
How many rays are contained in the
figure? Name them.
5 rays.
Names are:
𝐵𝐴
𝐵𝐶
𝐶𝐴 (or 𝐶𝐵)
𝐴𝐶 (or 𝐴𝐵)
𝐵𝐷

7. ANGLE
An angle is formed
by two rays with the
same endpoint.
▨ The rays are the
sides of the angle.
▨ The endpoint is
the vertex of the
angle.
How to Name It:
1. Named using the angle
symbol ∠ and a number.
OR
2. Named using the angle
symbol (∠) and the vertex
of the angle.
OR
3. Named using the angle
symbol (∠) and three
points on the angle. The
first point is on one side
of the angle, the second
point is the vertex of the
angle, and the third point
is the on the other side of
the angle.
Example:
∠3
∠𝑌
∠𝑋𝑌𝑍
∠𝑍𝑌𝑋

8. EXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLES
EXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLES
EXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLESEXAMPLES P8: Give all
possible names
for the given
angle.
∠𝐶
∠𝑆𝐶𝑁
∠𝑆𝐶𝐹
∠𝑁𝐶𝑆
∠𝐹𝐶𝑆
P9: Explain why
∠𝑆 is not an
appropriate
name for ∠1.
Point 𝑆 is the
vertex for both
∠1 and ∠2. The
name “∠𝑆” could
refer to either ∠1
or ∠2, so ∠𝑆
cannot be used to
name either
angles.
P10: Is ∠𝐹𝐸𝐷 a
possible name
for the figure at
the right?
No.
If an angle is named
with 3 letters, then
the vertex of the
angle must be in the
middle of the 3
letters. The vertex of
the angle is point 𝐷,
so correct names
would be ∠𝐸𝐷𝐹 or
∠𝐹𝐷𝐸.
P11: Give the
other possible
appropriate
names for ∠2.
∠𝑇𝑆𝑈
∠𝑈𝑆𝑇

9. Lesson 1-1 Homework posted on
OneNote and Blackboard. Link to
submit also on OneNote and
Blackboard.
Remember: You will take pictures of your
homework once you’ve finished and upload
those pictures using the link mentioned
above.
Due Tomorrow by 3:10pm or you will