Geometry Vocabulary

Angle

Made up of 2 rays joined together at a common point called a vertex.

The angle is

ABC

Circle

• The set of points on a plane at a certain distance, or radius, from a single point, the center

Lines that intersect at 90angles.

M

E

𝑴 ⊥ 𝑬

Perpendicular Lines

Two lines that intersect at a right angle (90°).Written as .AB PQ

Lines in the same plane that do not intersect.

WE

GO

𝑾𝑬 𝑮𝑶

Parallel Lines

Lines in a plane that do not share any points and never intersect.Written as AB PQ

Line Segment

A line with two endpoints.Written as AB

Point

Point A

or

Point B

An exact position or location in a given plane.

Is represented by a dot and named with a capital letter.

Line

The set of points between points in a plane and the infinite number of points that continue beyond the points.

Written as PQ

P

Q

Ray A line that has one endpoint and continues on forever in the opposite direction.

Right Angle

An angle that measures 90°.

Acute Angle

An angle measuring less than 90° but greater than 0°.

Obtuse Angle

An angle measuring greater than 90° but less than 180°.

Straight Angle

An angle measuring exactly 180°.

A triangle with no congruent sides.

A triangle with two congruent sides.

Points that lie in the same plane.

Points that lie on the same line.

AR M

A, R, & M are collinear points

Congruent

Figures are congruent if they have the same shape, size, lines, and angles.

Angles that have the same measure

B

E

B ≅ 𝑬

Two segments that have the same length.

OK

YA

𝑶𝑲 ≅ 𝒀𝑨

Have the same shape but not necessarily the same size.

3

45

6

8 10

Complementary Angles

Two angles that add up to 90 degrees.

12

30

60

Supplementary Angles

Two angles that add up to 180°.

1 2

20

160

Adjacent Angles

Two angles that share a common vertex and side.

SIDE BY SIDE

Two angles in the same plane with a common vertex and a

common side, but no common interior points.

12

1 & 2 are adjacent angles

To divide into two congruent parts.

L

K

M

𝑱𝑲 bisects LJM

J

The point that divides a segment into two congruent segments.

O BC

O is the midpoint of 𝑪𝑩

A closed plane figure formed by three or more segments such that each

segment intersects exactly two other segments only at their endpoints and

no two segments with a common endpoint are collinear.

A polygon that is both equilateral and equiangular.

Equilateral

•Having all sides the same length

Altitude

a line that extends from one vertex of a figure perpendicular to the opposite side, this is the height of figure.

Line of Symmetry

• the imaginary line where you could fold the image and have both halves match exactly

Perpendicular Bisector

•A line which cuts a line segment into two equal parts at a 90° angle

A

B C

A corner or point where lines, rays, polygons, or other geometric figures meet.

vertex

Vertical AnglesTwo angles directly across from each other that are congruent. They share a common vertex. E & G and H & F are vertical angles.

hf

e

g

Linear Pair

A linear pair is a pair of adjacent angles that are supplementary. For example, angle 1 and 2 in the figure below form a linear pair.