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Geometry Vocabulary
Lines and Angles Unit
Ms. Thomas
What is a point?
A point is an exact location in space represented by a dot/letter.
A
B
C
What is a line?
A line goes on forever in opposite directions.
K L
What is a line segment?
It includes two points, called endpoints.
A B
What is a midpoint?
A point on a line segment that divides it into two equal parts.
M
What is a ray?
A part of a line, with one endpoint, that continues forever in one direction.
T R
What are parallel lines?
Lines that will NEVER touch or intersect.
What are perpendicular lines?
Two lines that intersect and form 4 right angles.
What are intersecting lines?
A point where two lines cross/intersect.
What is a bisector?
A line, ray or segment which cuts another line segment or angle into two equal parts.
What is a perpendicular bisector?
A line which cuts a line segment into two equal parts at 90°.
Angles
What is an angle?
A shape, formed by two lines or rays diverging from a common point (the vertex).
What is a right angle?
A right angle is an angle that measures exactly 90°. It is displayed by using a square to label it.
What is an acute angle?
An angle that measure 89° or less. Think of it as “a cute” angle because it is so tiny.
What is an obtuse angle?
An angle that measures 91° to 180°. Think of an obtuse angle as “obese” because it’s measurement is so large.
What is a straight angle?
A straight line that measures EXACTLY 180°.
What is a reflex angle?
An angle whose measure is greater than 180° and less than 360°.
What is a full angle?
An angle whose measure is exactly 360°. A full circle.
What is a vertex?
The common endpoint of two or more rays or line segments.
What are vertices?
Vertices are more than one vertex.
Complimentary Angles
Angles with a sum of 90°.
Supplementary Angles
Angles with a sum of 180°
Complementary/Supplementary Trick
C comes before S in the alphabet 90 comes before 180 on a number line
Complementary = 90° Supplementary = 180°
