Geometry Vocabulary

What is Geometry? Geometry is the study of shapes They studied Geometry in Ancient Mesopotamia & Ancient Egypt Geometry is important in the art and construction fields

POINT A POINT is an exact location on a graph, shape or in “space”. We name the point with a letter. A ●

ENDPOINT An ENDPOINT is a point at the end of a ray or line segment.

Line vs Line Segment A LINE is a collection of points on a straight path. Extending in both directions and never, never, never ends. Lines that end are called LINE SEGMENTS. A AB B

RAY A RAY is part of a line, but it has one endpoint and the other end keeps going. A ● Endpoint

MIND POINT It Is a point located in the exact center of a line segment. A M B M is the midpoint of AB

CONGRUENT CONGRUENT means the “same”. CONGRUENT LINE SEGMENTS means two line segments are the same. A B C D ● ● AB = CD ● ●

Congruent Symbols What can be said about line segments AB and CD A B C D

Examples 2 5 4 A B C D E What is the length of line segment CD?

Perpendicular lines Two lines that meet at a 90 degree angle

Parallel Two lines that never meet

Intersecting Lines that just cross

Bisector A line that cuts another line in half( two equal pieces) at a 90 degree angle. A B Bisector

Angle Bisector A ray that cuts an angle in half ( two equal pieces). B

VERTEX A VERTEX is a fancy name for “angle” Two rays or lines that have the same endpoint make a VERTEX/angle VERTEX/angles are measured in “degrees” When two lines cross, they make vertex/angles The Corners of a square are its vertex/angles

Measure Symbol M Examples: M AB M ABC M DEF

PROTRACTOR We use a PROTRACTOR to measure vertex/angles in degrees

Degree Basic unit of measurement for an angle. Symbol ° Example: M ABC = 90°

Angles When 2 edges or sides meet. A Vertex ( common part).

ANGLES When you “name” an angle. The vertex/angle “letter/number” goes in the center of the label B A C If I wanted to know the measurement of Angle A…I would ask:” What is the measurement for BAC?” (Notice A is in the center)

4 TYPES OF ANGLES RIGHT ANGLES measure exactly 90 ° The “square” symbol means 90’

4 TYPES OF ANGLES ACUTE ANGLES are less than 90°

4 TYPES OF ANGLES OBTUES ANGLES are greater than 90 ° but less than 180 °

4 TYPES OF ANGLES STRAIGHT ANGLE is exactly 180 °