Vocabulary book review
Objectives
 Can you define and identify basic geometric terms?
Undefined Terms
 Undefined Terms: terms that do not have any actual size
Term
Definition
Naming Term
Point
A location in space, no actual
shape or size
By a capital letter
Point A
Line
Made up of two points and has no By any two points on
thickness or width; 1 dimension the line or small italic
letter
Line AB
Line l
Plane
A flat surface made up of points
that extends indefinitely in all
directions; 2 dimensions
By any three
noncollinear points or
large italic letter
Plane DMP
Plane L
Picture
A
Vocabulary
Term
Definition
Collinear
If points are on the same line, then
they are collinear
Coplanar
If points are on the same plane, then
they are coplanar
Intersection
Set of points in common for two or
more figures
Picture
Possibilities of Intersection of a Plane and a Line
(add to facts of line or plane)
 Three possibilities:
 Line passes through the plane—intersection is a point
 Line lies on the plane—intersection is a line
 Line is parallel to the plane—no common points
Intersection of Two Planes or Two Lines (add to facts
of lines and planes)
 Intersection of two lines is a point
 Intersection of two planes is a line
Examples
 Name a plane.
 Name a point.
 Name a line.
 Name three points that are collinear.
 What point do line j and line m intersect at?
 Two lines intersect in a ____________
 Two planes intersect in a ______________
 A line and a plane intersect in a _____________
Example
 How many planes are in the figure?
 Are points A,B,C coplanar?
 Are points A,B,C,F coplanar?
Example
 How many planes are labeled in the figure?
 Name the plane containing points E and C.
 Name the intersection of plane R and plane P.
 Name a point that is collinear to D and A.
 Name a point that is not coplanar to F, D, and G.
Example
 Draw two planes not intersecting.
 Draw a line on a plane.
 Draw a line intersecting a plane.
 Draw three lines that are not coplanar.
Segment Vocabulary
Term
Definition
Naming Terms
Line Segment
Part of a line that has two
endpoints
Segment AB
Betweenness of
Points
If B is between points A and C
(A-B-C), then A, B , and C are
collinear and AB+BC=AC
Relationship of points
Midpoint of a
Segment
The point halfway between
the endpoints of the
segment
If A-B-C and AB=BC then B is
the midpoint of AC
Congruent
Segments
If two segments are
congruent then they have
the same length
Segment Bisector Any segment, line, or plane
that intersects a segment at
its midpoint
AB
≅
𝐴𝐵 ≅ 𝐶𝐷
Picture
Angle Vocabulary
Term
Definition
Naming the Term/
Symbol
Ray
A part of a line that has one endpoint and
extends in one direction
Ray AB
𝐴𝐵
Beginning letter has to
be the endpt
Angle
Formed by two noncollinear rays that have a
common endpoint
Either use 3 or 1 letter
or 1 number
Sides of the angle are rays
Vertex of the angle is the common endpoint
Angles are measured in degrees
Order matters in
naming an angle!
Symbol for angle
Name this
angle.
Picture
Angle Terms and Types
Term
Definition
Right angle
If an angle measures 90 degrees then it is a right
angle
Acute Angle
If an angle measures less than 90 degrees then it is
an acute angle
Obtuse Angle
If an angle measures more than 90 degrees then it is
an obtuse angle
Straight Angle
If an angle measures 180 degrees then it is a straight
angle
Congruent Angles
If two angles are congruent then they have the same
measure
Angle Bisector
If a ray divides an angle into two congruent angles
then it bisects the angle
Picture
Type equation here.
Examples
1) Find the length of segment EG.
●
7.5
E
●
F
3
●
G
2) Find the length of segment AB. AC=15
●
A
●
9.5
●
B
C
3) Find the midpoint of AB.
4) Find x, if B is between A and C. AB=2x, BC=3x, and AC=15.
Measuring an Angle
 Use a protractor
Examples
 1)Name all angles with vertex B.
 2)Name the sides of angle 5.
 3)Write another name for angle 6.
 4)Name a point on the exterior of Angle GBA.
 5) Are ray BD and ray BG the same ray?
A
G
5 B6
E
F
D
Classwork
 Complete practice sheet 1.2 and 1.3
Special Angle Pairs
Term
Definition
Adjacent Angles
If two angles have a common vertex and
a common side then they are adjacent
Linear Pair
If there is a pair of adjacent angles with
noncommon sides that are opposite
rays, then there is a linear pair formed
Vertical Angles
If there are two nonadjacent angles
formed by two intersecting lines, then
vertical angles are formed
Vertical angles are congruent
Picture
Angle Relationships
Term
Definition/Relationsh
ip
Complementary
Angles
If two angles add up to 90
degrees, then they are
complementary
Supplementary
Angles
If two angles add up to 180
degrees then they are
supplementary
Linear pair angles are
supplementary
Picture
Types of Lines
Term
Definition
Perpendicular
Lines
Lines that intersect to form
four right angles. All angles
are congruent and adjacent.
Right angle symbol indicates
perpendicular.
Coplanar lines that do not
intersect.
Parallel Lines
Skew Lines
Lines that do not intersect
and are not coplanar.
Symbol
Picture
Examples
 Match the following term with the appropriate picture
Adjacent angles
Linear Pair
Vertical Angles
Complementary Angles
Supplementary Angles
Perpendicular Lines
Examples
 Name two adjacent angles, two vertical angles, two supplementary angles,
and a linear pair
 Find x.
Vocabulary
Term
Definition
Polygon
A closed figure formed by a finite number of coplanar
segments called sides
Convex
A polygon (which is straight-sided) is convex if there are no
"dents" or indentations in it (no internal angle is greater than
180°)
Concave
A polygon (which is straight-sided) is concave if there are
"dents" or indentations in it (where the internal angle is greater
than 180°)
(Caves in)
Regular
All sides are congruent and all angles are congruent
Triangle
A three sided polygon
Angles add to 180 degrees
Picture
Types of Triangles By Angles
Name by Angles
Picture
Acute Triangle
3 Acute angles
Equiangular Triangle
3 congruent angles
Obtuse Triangle
One obtuse angle
Right Triangle
One right angle
Types of Triangles By Sides
Names by Sides
Picture
Equilateral Triangle
3 congruent sides
Isosceles Triangle
2 congruent sides
Scalene Triangle
No congruent sides
Interpreting Diagrams
Can be Assumed
Cannot be Assumed
All points are coplanar
Perpendicular lines: BX
A, X, D are collinear
Congruent Angles: Angle BXC≅ CXF
FX
BX, FX, DX, AX, GX, EX intersect at X
X is between A and D
E is in the interior of angle GXD
Angle AXG and Angle GXE are adjacent
Angle AXB and Angle BXD are supplementary
Congruent Segments: AX≅ XD