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Point

A location represented by a dot

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Line

An infinate set of points extending endlessly in both directions

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Plane

Set of points that form a flat surface that extends infinitely in both directions

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Collinear

Points that are on the same line

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Non-collinear

Points that are not on the same line

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Betweenness

B is between A and C if and only if A, B, C are distinct collinear points and AB + BC = AC

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Coplanar

Points that are on the same plane

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Parallel Lines

2 lines that never intersect (in same plane)

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Perpendicular Lines

2 lines that intersect to form right angles (in same plane)

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Line segment

Set of points consisting of two points on a line, called endpoints , and all points on the line between the endpoints

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Length/Measure of a Segment

Distance between its endpoints

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Congruent Segments

Segments that have the same length/measure

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Midpoint

Point on a segment that divides the segments into 2 congruent segments

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Bisector of a Segment

Line, ray or a segment that intersects a segment at its midpoint

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Ray

Part of a line consisting of an endpoint and extending infinitely in the other direction

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Opposite Rays

2 rays of the SAME LINE with a common endpoint.

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Angle

The union of 2 rays having the same endpoint (vertex)

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Straight Angle

A 180 degree angle (line)

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Acute Angle

Between 0 degrees and 90 degrees

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Right Angle

A 90 degree angle

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Obtuse Angle

between 90 degrees and 180 degrees

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Congruent Angles

Two angles that have the same measure

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Angle Bisector

Ray whose endpoint is the vertex of the angle and it divides the angle into 2 congruent angles

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Complementary Angles

A pair of angles, the sum of whose degree measures 90 degrees

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Supplementary Angles

A pair of angles, the sum of whose degree measures 180

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Linear Pair

2 adjacent angles whose sum is a straight angle

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Vertical Angles

Angles formed across from one another and are congruent

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Adjacent Angles

Two angles who share a common vertex, common side (ray), but no common interior points

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Polygon

A closed figure in a plane that is the union of line segments such that the segments only intersect at their endpoints and no segments sharing a common endpoint are collinear.

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Triangle

A polygon that has exactly 3 sides

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Scalene triangle

Triangle that has exactly had no cogruent sides

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Isosceles Triangle

Triangle that has 2 congruent sides

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Equilateral Triangle

Triangle that has 3 congruent sides

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Acute Triangle

Triangle that has 3 acute angles

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Equiangular Triangle

Triangle that has 3 congruent angles

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Right Triangle

Triangle that has a right angle

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Obtuse Triangle

Triangle that has an obtuse angle

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Parallel Lines

Lines in the same plane that have no points in common OR all points in common.

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Altitude

(height) Line segment drawn from a vertex to the opposite side and is perpendicular to it.

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Median

Line segment drawn from a vertex to the midpoint of the opposite side.

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