Geometry Vocabulary

Reference Chart

Point

• Write using a Capital letter

  • Ex) A

Line

• A straight path of points that extends forever

• Two points ONLY

• Order doesn't matter

  • Ex) Line BC

Endpoint

• The point at the end of a line segment or the starting point of a ray

• Write using Capital letter

  • Ex) D, E

Line Segment

• A part of a line with 2 endpoints

• Use two endpoints only

• Order doesn't matter

  • Ex) Line DE

Ray

• A part of a line that has one endpoint and extends forever in ONE direction

• Two points

• 1st point MUST BE ENDPOINT

• 2nd point is any point that the ray passes through

  • Ex)

Vertex

• Endpoint of the 2 rays that form an angle or 2 line segments to form a corner

• Only the point

Angle

• The figure formed when 2 rays meet at a common endpoint

• Using VERTEX ONLY, three points (VERTEX in middle), or a given number

Right Angle

• EXACTLY 90*

Obtuse Angle

• GREATER THAN 90*

• Less than 180*

Acute Angle

• Less than 90

• More than 0*

Straight Angle

Angle that is EXACTLY 180*

Parallel Lines

• 2 lines that never intersect

  • Ex) l l

Perpendicular Lines

• 2 lines that intersect to form right angles

• MUST BE 90*

Adjacent Angles

• (Side by Side)

• Angles that share a common ray

• And a common Vertex

Complementary Angles

• Two angles whose angle measurements add up to 90*

Supplementary Angles

• Two angles whose angle measurements add up to 180*

Vertical Angles

• Angles created by INTERSECTING two lines

• Forms X

Linear Pair

• Two adjacent angles whose non-common sides Form a straight line

• Forms a T

• Supplementary Angles

Angle Bisector

• Ray that bisects an angle

• Divides it into two equal angles

• Ex) 45+45