###
Polygon

a closed figure with 3 or more line segments

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quadrilateral

a polygon with four sides

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pentagon

a polygon with five sides

###
angles

the figure formed by 2 rays with the same endpoint

###
octagon

a polygon with eight sides

###
decagon

a polygon with 10 sides

###
scalene

a shape with no congruent sides

###
isosceles

a shape with more than 1 congruent sides

###
equilateral

a polygon with all sides congruent

###
right

a shape or figure with a 90 degree angle

###
parallelogram

a quadrilateral whose opposite sides are parallel

###
rectangle

a parallelogram with four right angles

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trapezoid

a quadrilateral with one pair of parallel sides

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square

a rectangle which is equilateral

###
degrees

the basic unit by which angles are measured

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vertex

the intersection of the two sides of an angle i

###
points

a dot that represents a location in a plane or space

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line

a straight path of points that extend forever in opposite directions

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plane

a flat surface that extends forever in all different directions

###
ray

part of a line that has 1 endpoint and extends forever in only 1 direction

###
line segment

part of a line consisting of 2 endpoints and all the points between them

###
congruent

shapes that are exactly the same

###
intersection

the set of points that are common to 2 or more lines

###
parallel

lines in the same place but do not intersect

###
vertex

the point at the corner with an angle, plane angle, or solid figure

###
measure

the measure of something (angle)

###
protractor

to use and approximate the measure of an angle

###
perpendicular

2 lines that meet at right angles

###
complementary

2 angles that if the sum of their measure is 90 degrees

###
supplementary

2 angles and if the sum of their measure is 180 degrees

###
vertical angles

angles that are formed by intersecting lines (angles across from each other)

###
corresponding angles

angles that are formed by intersecting lines (horizontal lines that form angles)

###
skew lines

in 3-D world, lines don't cross but not parallel

###
scalene triangle

all sides have different lengths

###
isosceles triangle

at least 2 sides have to be the same

###
equilateral triangle

all 3 sides have to be the same (60 degrees)

###
acute triangle

if all 3 angles are acute

###
obtuse triangle

if 1 of the angles are obtuse

###
right triangle

if one of the angles is a right angles

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