Download Definition of a Point

Definitions and Examples of
Geometric Terms
Definition of a POINT
A point has no size
and has only a
location in space.
It is represented by a
dot and named by
capital letters.
A•
C•
B•
Definition of a LINE
 Example
A line is a straight
arrangement of points.
It has length but no
thickness and extends
forever in both
directions.
 Name each line two different ways
Lines are named using
two points on the line.
 Draw and label each line
Definition of a PLANE
A plane has length and
width but no thickness.
It is a flat surface that
extends forever.
 Example
Definition of a LINE SEGMENT
A line segment consists
of two points called
endpoints and all the
points between the
endpoints.
 Example
 Name each line segment two
different ways
 Draw and label each line segment
Definition of a RAY
 Example
A ray is half a line.
Rays are named by its
endpoint and a point on
the ray.
 Name each ray two different ways
 Draw and label each ray
Definition of an ANGLE
An angle is two rays that
share a common
endpoint where the two
rays do not line on the
same line.
VERTEX OF AN ANGLE
The common endpoint
of two rays that make an
angle.
SIDES OF AN ANGLE
The two rays that form
an angle.
 Example
 Name each angle two different
ways
 Draw and label each angle
Measurements of an Angle
Degree meaure range
from 0 to 360 degrees
Full rotation is a circle:
360 degrees
Half rotation is a line:
180 degrees
Quarter rotation is 90
degrees
 Examples
How to measure an Angle
Place the center mark of
the protractor on the
vertex of the angle
Rotate the “zero-edge of
the protractor to line up
with one side of the
angle
Read the measure of the
angle on the protractor’s
scale at the point where
the other side crosses.
 Exercise Set A
Marking angles and segments
with same measures
Angles with the same
measure are marked
with an arc and the same
number of slashes.
Segments with the same
lengths are marked with
the same number of
slashes
 Exercise Set D
Classification of Angles
 Examples
Right angle: Angle with
measure 90.
Acute angle: Angle with
measure between 0 and
less than 90
Obtuse angle: Angle
with measure greater
than 90 and less than
180.
Definition of Midpoint of a Segment
and an Angle Bisector
Midpoint of a segment:
The point that divides
the segment into two
segments of equal
measure.
Angle bisector:
The ray that divides an
angle into two angles of
equal measure.
 Examples
Definition of Collinear and Coplanar Points
Collinear points:
Points all on one line.
Coplanar points:
Points all on one plane.
 Examples
Definition of Parallel and Perpendicular Lines
Parallel lines
Lines on the same plane
that do not intersect.
Perpendicular lines
Two Lines that intersect
to form right angles.
 Examples
Definition of Pair of Complementary
and Supplementary Angles
 Examples:
Pair of complementary angles
Two angles that equal 90
degrees.
Pair of supplementary angles
Two angles that equal 180
degrees
Definition of Polygons
Polygons
A closed geometric figure in a
plane formed with at least three
sides that are segments. The
sides intersect only at their
endpoints. No two adjacent sides
are collinear.
Convex Polygons
No segment connecting two
vertices is outside the polygon
Concave Polygons
At least one segment connecting
two vertices is outside the
polygon
 Examples:
Classification of Polygons
 Examples:
Number of sides
3 Triangle
4 Quadrilateral
5 Pentagon
6 Hexagon
7 Heptagon
8 Octagon
9 Nonagon
10 Decagon
Naming Polygons; Diagonals of Polygons
 Examples:
Naming Polygons
Use the letters in consecutive
order.
Diagonals of Polygons
A segment that connects
nonconsecutive vertices of a
polygon.
Special Polygons
 Examples:
Equilateral Polygons
All sides are congruent (same
measure).
Equiangular Polygons
All angles are congruent.
Regular Polygons
All sides and angles are
congruent.
Definition of Triangles
 Examples:
Right Triangle
One right angle
Acute Triangle
All acute angles
Obtuse Triangle
One obtuse angle
Definition of Triangles
 Examples:
Scalene Triangle
No sides are congruent
Isosceles Triangle
Two sides are congruent
Equilateral Triangle
All sides are congruent
Median and Altitude of a Triangle
 Examples:
Median of a Triangle
A segment from the midpoint
of one side of a triangle to the
opposite vertex.
Altitude of a Triangle
The perpendicular segment
from a vertex of a triangle to the
line containing the opposite
side.
Definition of Special Quadrilaterals
Quadrilateral
A 4-sided polygon
Rectangle
A quadrilateral with four right
angles.
Square
A quadrilateral with four right
angles four congruent sides .
 Examples:
Definition of Special Quadrilaterals
 Examples:
Trapezoid
A quadrilateral with exactly one
pair of parallel sides.
Parallelogram
A quadrilateral with both pairs
of opposite sides parallel.
Rhombus
A quadrilateral with four
congruent sides.