Point

An exact location in space.

• A

Label: Point A

Line

A set of points continuing without end in both directions.

• • B C

Label: BC

Segment

Two points and the straight path between them.

• • D E

Label: DE

Endpoint

The point at the end of a segment or ray.

• • D E

Label: Point D or Point E

Ray

A set of points that has one endpoint and that extends without end in one

direction.

• • F G

Label: FG**The first letter in the label is the endpoint of the ray.

Plane

A flat surface that extends without end in all directions.

H

Label: Plane H

Parallel Lines

Lines in a plane that never touch.

• • J K

• • L M

Label: JK and LM

Intersecting Lines

Lines that meet at a point.

• • N R

• • Q P

Label: NP and QR

Perpendicular Lines

Intersecting lines that form right angles (90° angles).

• S

• • U V

• T

Label: ST and UV

Skew Lines

Lines that are in two different planes.

• T • S

• • U V

Label: ST and UV

Angle

Figure formed when two rays meet at a common endpoint.

C •

• • A B

Label: A, BAC, or CAB

Vertex

The endpoint where two rays meet.

C •

• • A B

Label: Point A

Right Angle

The measure of the angle is 90°.

• D

• • E F

Label: E, DEF, or FED

Straight Angle

The measure of the angle is 180°.

• • • G H I

Label: H, GHI, or IHG

Obtuse Angle

The measure of the angle is between 90° and 180°.

K •

• • J L

Label: J, KJL, or LJK

Acute Angle

The measure of the angle is between 0° and 90°.

N •

• • M P

Label: M, NMP, or PMN

Complementary Angles

Two angles whose measures add up to 90°.

R • • S

• • Q T

Label: RQS and SQT

Supplementary Angles

Two angles whose measures add up to 180°.

X•

• • • W V Y

Label: WVX and XVY

Adjacent Angles

Angles that have a common vertex and a common side between them.

• • B C

Z• • D

A •

Label: BZC and CZD

Vertical Angles

Angles formed by two intersecting lines and sharing only a vertex.

• • J K

M• • L

N •

Label: JMK and NML

Circle

A plane figure with all points the same distance from a given point called the

center.

K•

Label: Circle K

Center

Point in the circle that is exactly in the middle.

K•

Label: Point K

Chord

A segment with both endpoints on the circle.

D•

• E

Label: DE

Diameter

In a circle, a segment that passes through the center and has both

endpoints on the circle.G•K•H•

Label: GH

Radius

In a circle, a segment that connects the center of the circle with a point on the

circle.J•K•

Label: JK

Central Angle

An angle with its vertex at the center of a

circle.L•K•

Label: LKM

•M

Arc

Part of a circle.

L•

K•

Label: LM

•M

Polygon

A closed figure made of three or more segments.