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Point

names a location and has no size

Line

a straight path that has no thickness and extends forever

Plane

a flat surface that has no thickness and extends forever

Collinear

points that lie on the same line

Coplanar

points that lie on the same plane

Segment

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

Endpoint

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

Ray

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

Opposite rays

two rays that have a common endpoint and form a line

Postulate (axiom)

a statement that is accepted as true without a proof.

Coordinate

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

Distance

the absolute value of the difference of the coordinates

Congruent Segments

segments that have the same length

Construction

a way of creating a figure that is more precise

Midpoint

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

Bisects

divides

Segment Bisector

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

Angle

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

Vertex

an angle's common endpoint

Interior of an angle

the set off all points between the sides of the angles

Exterior of an Angle

the set of all points outside the angle

Acute Angle

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

Right angle

an angle that measures ninety degrees

Obtuse Angle

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

Straight Angle

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

Congruent Angles

angles that have the same measure

Angle Bisector

a ray that divides an angle into two congruent angles

Adjacent Angles

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

Linear Pair

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

Complementary Angles

two angles whose measures have a sum of ninety degrees

Supplementary Angles

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

Vertical Angles

two nonadjacent angles formed by two intersecting lines

Perimeter

the sum of the side lengths of the figure

Area

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

Base

any side of a triangle

Height

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

Diameter

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

Radius

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

Circumference

the distance around the circle

Pi

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

Coordinate Plane

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

Legs

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

Hypotenuse

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

Transformation

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

Preimage

the original figure

Image

a figure after transformation

Reflection

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

Rotation

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

Translation

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