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A point is a location on plane usually represented by a dot

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a line is a never-ending straight line.

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a segment is the part of a line containing two endpoints and all the points between them.

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a ray is the part of a line that extends indefinately in one direction from a fixed point.

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a plane is a 2D flat suface that extends in all directions.

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Collinear means they lie on the same line. ex:  A and D are collinear in the picture above.

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Coplanar means they are found on the same plane. Ex: points G, E, F and A.

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Angles are figures formed by two rays with a common endpoint.

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A Midpoint is on a line segment, the point that is halfway between the endpoints.

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A Bisector is a ray whose endpoint is vertex of the angle; inside the angle

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congruent is having the same measure. Ex: in the picture all sides of the angle is congruent.

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Vertex is the common endpoint of the ray forming the angle.

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Acute Angle is an angle with a measure greater than 0 degrees but less than 90 degrees.

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An Obtuse Angle is an alngle that measures more than 90 degrees but less than 180 degrees.

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A right Angle is a angle that measures exactly 90 degrees.

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A Straight Angle is an angle that measures 180 degrees

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Complementary Angles are two angles with the sum of their measure 90 degrees. 

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Supplementary Angles are two angles with the sum of their measure 180 degrees.

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Vertical Angles are opposite angles formed by the intersection of two or more lines.

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Adjacent Angles are angles that have the same vertex, share a common side and do not overlap.

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Linear Pairs are two supplementary adjacent angles formed by two intersecting lines.

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Perpendicular Lines are lines which meet to form right angles.

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A Polygon is a simple closed figue in a plane formed by three or more line segments.

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A Triangle is a polygon with three sides.

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A Quadrilateral is a polygon with four sides.

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A pentagon is a five-sided polygon.

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A hexagon is a six-sided polygon.

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A Octagon is a eight-sided polygon.

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A Decagon is a ten-sided polygon.

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A N-gon is a polygon with n sides.

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A Concave Polygon is a polygon for which at least one of it's diagonals lie outside of the polygon.

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A Convex Polygon has all diagonals inside of the polygon.

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A Regular polygon has all sides and angles congruent.

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An Irregular Polygon does not have all sides and angles equal.

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A Diagonal is a straight line that goes from one corner to another but not an edge. 

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Sides of a Polygon are segments that form a closed figure.

Sides of an Angle are two rays that form an angle

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A perimeter is the distance around a closed geometric figure.