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Point

names a location and has no size

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Line

a straight path that has no thickness and extends forever

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Plane

a flat surface that has no thickness and extends forever

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Collinear

points that lie on the same line

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Coplanar

points that lie on the same plane

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Segment

the part of a line consisting of two points and all the points between them

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Endpoint

a point at one end of a segment or the starting point of a ray

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Ray

a part of a line that starts at an endpoint and extends forever in one direction

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Opposite rays

two rays that have a common endpoint and form a line

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Postulate (axiom)

a statement that is accepted as true without a proof.

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Coordinate

a point that corresponds to one and only one number on the ruler

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Distance

the absolute value of the difference of the coordinates

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Congruent Segments

segments that have the same length

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Construction

a way of creating a figure that is more precise

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Midpoint

the point that bisects, or divides the segment into two congruent segments

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Segment Bisector

any ray, segment, or line that intersects a segment at its midpoint.

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Angle

a figure formed by two rays, or sides, with a common endpoint called a vertex

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Vertex

an angle's common endpoint

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Interior of an angle

the set off all points between the sides of the angles

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Exterior of an Angle

the set of all points outside the angle

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Acute Angle

an angle that measures grater than zero degrees and less than ninety degrees

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Right angle

an angle that measures ninety degrees

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Obtuse Angle

an angle that measures grater than ninety degrees and less than one-hundred-eighty degrees

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Straight Angle

an angle formed by two opposite rays and measures one-hundred-eighty degrees

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Congruent Angles

angles that have the same measure

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Angle Bisector

a ray that divides an angle into two congruent angles

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Adjacent Angles

two angles that are in the same plane with a common vertex and a common side, but no common interior points

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Linear Pair

a pair of adjacent angles whose non-common sides are opposite rays

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Complementary Angles

two angles whose measures have a sum of ninety degrees

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Supplementary Angles

two angles whose measures have a sum of one-hundred-eighty degrees

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Vertical Angles

two nonadjacent angles formed by two intersecting lines

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Perimeter

the sum of the side lengths of the figure

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Area

the number of non-overlapping square units of a given size that exactly covers the figure

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Base

any side of a triangle

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Height

a segment from a vertex that forms a right angle with a line containing the base

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Diameter

a segment that passes through the center of the circle and whose endpoints are on the circle

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Radius

a segment whose endpoints are the center of the circle and a point on the cicle

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Circumference

the distance around the circle

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Pi

ratio of a circle's circumference to its diameter (3.14)

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Coordinate Plane

a plane that is divided into four regions by a horizontal line

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Legs

in a right angle triangle, the two sides that form the right angle

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Hypotenuse

the side across from the right angle that stretches from one leg to the other

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Transformation

a change in the position, size, or shape, of a figure

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Preimage

the original figure

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Image

a figure after transformation

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Reflection

a transformation across a line. Each point and its image are exactly the same distance from the line

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Rotation

a transformation about a point. Each point and its image are the same distance from that point

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Translation

a transformation in which all the points of a figure move the same distance, in the same direction

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