Download Geometry Glossary TERM DEFINITION NOTATION DIAGRAM

Geometry Glossary
TERM
DEFINITI
ON
Collinear
points lie on
the same
line.
NOTATION
DIAGRAM
N/A
Collinear
Coplanar
points or
lines lie on
the same
plane.
N/A
A line
segment is
that part of
a line that
consists of
two points,
called
endpoints,
and all the
points
between
them.
A line
segment is
designated

AB .
Coplanar
Line
Segment
The measure
of a line
segment is
designated
AB
Points A, B, and C are collinear.
Points K, L, M are coplanar; Points O, P, and N are
coplanar.
Endpoint
Angle
An endpoint
is a point at
the end of a
segment or
ray.
N/A
An angle is
formed by
two noncollinear
rays that
share a
common
endpoint,
designated
∠ABC
or ∠D.
A vertex is
the common
endpoint of
the rays
forming the
angle.
An angle is
designated
∠ABC
or ∠D.
Vertex
Congruent
Congruent
(angles,
segments,
polygons,
circles,
solids) are
identical in
size and
shape.
The measure
of an angle
is
designated
as m∠ABC or
m∠B.
N/A
However,
when angles
are
identified
using three
points, the
middle point
is the
vertex. For
example, the
vertex of
∠ABC is
point B.
Example:
∠ABC ≅
∠DEF
Equal
measures of
segments or
angles are
designated
AB = CD or
m∠ABC =
m∠D.
Midpoint
Bisector
Right
Angle
Acute
Angle
A midpoint
of a
segment is a
point that
divides a
segment
into two
congruent
segments.
A bisector
is a line,
segment, or
ray that
divides a
figure into
two
congruent
figures.
N/A
A right
angle is an
angle that
measures
90°.
N/A
An acute
angle is an
angle whose
measure is
between 0°
and 90°.
N/A
Point B is the midpoint of ̅̅̅̅
𝐴𝐶
N/A
̅̅̅̅
𝐴𝐷 is an angle bisector of∠BAC
∠EBD is acute
Obtuse
Angle
Vertical
Angles
Linear Pair
of Angles
Complement
ary
Angles
Supplementa
ry
Angles
An obtuse
angle is an
angle whose
measure is
between
90° and
180°.
A pair of
vertical
angles is a
pair of nonadjacent
angles
formed by
two
intersecting
lines.
N/A
A linear
pair of
angles
consists of
two
adjacent
angles
whose sum
is 180°.
A pair of
complement
ary angles
is a pair of
angles
whose sum
is 90°.
N/A
∠AEC and ∠DEB are vertical angles.
∠AED and ∠CEB are vertical angles.
Angle ABC and Angle CBD are a linear pair
N/A
∠ABD and ∠CBD are complementary
A pair of
supplement
ary angles
is a pair of
angles
whose sum
is 180
N/A
∠ACD and ∠DCB are supplementary
N/A
Polygon
Consecutive
Angles
Consecutive
Sides
Convex
Polygon
A polygon is
a closed
figure in a
plane
formed by
connecting
line
segments
endpoint to
endpoint
Consecutive
angles in a
polygon
share one
side of the
polygon.
Common
polygon
names:
triangles,
quadrilateral
, pentagon,
hexagon,
heptagon,
octagon,
nonagon,
decagon,
dodecagon.
N/A
Consecutive
sides in a
polygon
share one
vertex of
the polygon.
N/A
A convex
polygon has
all of its
diagonals
within the
polygon.
N/A
∠DAB and ∠ABC are consecutive
∠ABC and ∠BCD are consecutive
̅̅̅̅
𝐴𝐵 and ̅̅̅̅
𝐵𝐶 are identified as consecutive sides
̅̅̅̅
𝐵𝐶 and ̅̅̅̅
𝐶𝐷 are identified as consecutive sides
̅̅̅̅
𝐶𝐷 and ̅̅̅̅
𝐴𝐷 are identified as consecutive sides
̅̅̅̅ and ̅̅̅̅
𝐴𝐷
𝐴𝐵 are identified as consecutive sides
Concave
Polygon
Diagonal
Equilateral
Equiangular
Regular
Polygon
A concave
polygon has
at least one
diagonal
lying
outside the
polygon.
A diagonal
of a polygon
is a segment
that
connects
two nonconsecutive
vertices.
N/A
A polygon in
which all
sides are
congruent is
an
equilateral.
N/A
A polygon in
which all
angles are
congruent is
an
equiangular
polygon.
N/A
A regular
polygon is
equilateral
and
equiangular.
Diagonals
are line
segments.
̅̅̅̅
𝐴𝐶 , ̅̅̅̅
𝐵𝐸 , and ̅̅̅̅
𝐵𝐷 are all diagonals
Regular polygons
Perpendicula
r
Parallel
Lines
Right
Triangle
Perpendicul
ar lines,
segments,
rays or
planes
intersect at
right angles
to each
other.
Parallel
lines, in the
same plane,
are
equidistant
from each
other.
Parallel
lines never
intersect.
A right
triangle is a
triangle
that has a
right (90
degree)
angle.
̅̅̅̅
𝐷𝐸 ⊥ ̅̅̅̅̅
𝐹𝐺
̅𝐻𝐼
̅̅̅ ∥ ̅̅̅̅
𝐾𝐽
N/A
̅̅̅̅
𝐷𝐸 ⊥ ̅̅̅̅̅
𝐹𝐺
Acute
Triangle
Obtuse
Triangle
Scalene
Triangle
Equilateral
Triangle
Isosceles
Triangle
Trapezoid
An acute
triangle is a
triangle
that has
three acute
angles.
An obtuse
triangle is a
triangle
that has
one obtuse
angle.
A scalene
triangle is a
triangle
with no
congruent
sides.
An
equilateral
triangle is a
triangle
that has
three
congruent
sides.
An isosceles
triangle is a
triangle
that has at
least two
congruent
sides.
A trapezoid
is a
quadrilatera
l with
exactly one
pair of
parallel
sides.
N/A
N/A
N/A
N/A
N/A
N/A
Kite
Parallelogra
m
Rhombus
Rectangle
Square
A kite is a
quadrilatera
l with two
distinct
pairs of
consecutive
congruent
sides.
A
parallelogra
m is a
quadrilatera
l with two
pairs of
parallel
sides
A rhombus
is a
quadrilatera
l with four
congruent
sides.
N/A
A rectangle
is a
quadrilatera
l with four
right angles.
N/A
A square is
a regular
quadrilatera
l; it has
four
congruent
sides and
four right
angles.
N/A
N/A
N/A
Circle
Diameter
Arc
Semicircle
A circle is a
set of
points a
given
distance
(radius)
from a given
point
(center) in
the plane.
Circles are
identified by
their center.
For example,
the image is
of Circle A,
denoted by
“a circle
with a dot in
the center”
A.
A diameter
is a segment
with
endpoints
on the
circle that
contains the
center of
the circle.
An arc of a
circle is
that part of
the circle
that
consists of
two points
on the
circle and
all the
points
between
them. The
two points
are called
endpoints.
A semicircle
is an arc of
a circle
whose
endpoints
are the
endpoints
of a
diameter.
The
diameter is
a line
segment
identified by
its
endpoints.
AB is a diameter
N/A
The part of the circle between B and C is an arc.
N/A
Chord
A chord is a
segment
whose
endpoints
lie on the
circle.
BC is a
chord of
Circle A