###
point

a location in space; it has no size

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line

a series of points that extends in opposite directions without end

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plane

a flat surface with no thickness. It contains many lines and extends without end in the directions of all its lines

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segment

part of a line; it has two endpoints.

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ray

part of a line; it has exactly one endpoint. Name its endpoint first

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parallel lines

two lines that lie in the same plane and have no points in common

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intersecting lines

lines that lie in the same plane and have exactly one point in common

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skew lines

lines that lie in different planes; they are not parallel and do not intersect

###
acute angle

an angle that is less than 90˚

###
obtuse angle

an angle that is greater than 90˚ and less than 180˚

###
straight angle

an angle that is equal to 180˚

###
right angle

an angle that is equal to 90˚

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adjacent angles

angles that share a vertex and a side but have no points in their interiors

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vertical angles

angles formed by two intersecting lines and are opposite each other. The opposite angles have the same measure

###
supplementary angles

the sum of the measure of two angles equals 180˚

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complementary angles

the sum of the measure of two angles equals 90˚

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transversal

a line that intersects two other lines in different points

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corresponding angles

angles that lie on the same side of the tranversal and in the same relative position

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alternate interior angles

angles between a pair of lines and on the opposite sides of the transversal

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vertex

the point of intersection of two sides of an angle or figure

###
perpendicular lines

lines that intersect to form right angles

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