###
Square

4 equal sides. 90 degree angles.

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Rectangle

quadrilateral. 90 degree angles.

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Quadrilateral

4-sided polygon

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Perimeter

distance around a figure

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Area

number of square units it takes to cover a figure

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Height

the line that makes a 90 degree angle with the base

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Right Angle

90 degree angle

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Acute Triangle

3-sided polygon, 1 angle greater than 90 degrees

###
Right Triangle

3-sided polygon. One 90 degree angle.

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Isosceles Triangle

3-sided polygon. 2 congruent sides.

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Equilateral Triangle

3-sided polygon. 3 congruent sides. 3 60 degree angles.

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Scalene Triangle

3-sided polygon. No congruent sides

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Leg

the 2 sides that make the right angle in a right triangle

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hypotenuse

side opposite the right angle in a right triangle

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parallelogram

4-sided quadrilateral. 2 pairs of parallel lines

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parallel lines

lines that will never intersect

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trapezoid

4-sided quadrilateral. 1 pair of parallel lines

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congruent

same size, same shape

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rhombus

4 equal-sided polygon

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segment

line between two points

###
vertex or vericies

the point where 2 lines meet

###
polygon

many-sided figure, closed, straight line segment

###
regular polygon

polygon with congruent sides and congruent angles

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irregular polygon

polygon without all congruent sides

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straight angle

angle measuring 180 degrees

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circle

infinite set of points equidistant from a centerpoint

###
diameter

distance across a circle through the center point

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pi

ratio of circumference of a circle to its diameter, irrational; = 3.14

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circumference

distance around a circle

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semi-circle

half of a circle

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complementary angles

angles whose sum equals 90 degrees

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Supplementary angles

angles whose sum equals 180 degrees

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interior angle

angles inside of a polygon

###
exterior angle

angle made when you extend one of the sides of the polygon outside from the polygon

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