Geometry Dictionary

Created by BonhommeNarchel 

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41 terms

Translation

A slide

Rotation

A turn

Reflection

A flip

A plane

Flat surface extending forever in all directions

A line

Straight path that extends forever in both directions

Line segment

Straight path between two endpoints

A angle

A figure formed by two rays that begin at the same point

Vertex

End point

A point

Exact location in space

Polygon

Closed figure formed by line segments joined only a their endpoints

Parallel lines

Lines that do not cross

Perpendicular lines

Lines that cross at 90 degree angle

Hexagon

Polygon with six sides

Octagon

Polygon with eight sides

Decagon

Polygon with ten sides

Right angle

Angle that is 90 degrees

Regular polygon

All sides congruent and all angles congruent

Diagonal

A line segment that joins two vertices of a polygon but it not a side

Obtuse angle

Greater than 90 degrees and less than 180 degrees

Acute angle

Angle less than 90 degrees

Nonagon

Polygon with nine sides

Heptagon

Polygon with seven sides

Pentagon

Polygon with five sides

Equilateral triangle

Three sides that have the same length

Isosceles triangle

Two sides that have the same length

Scalene triangle

No sides that have the same length

Acute triangle

Less than 90 degrees

Right triangle

90 degrees angle

Obtuse triangle

Greater than 90 degrees

Trapezoid

One pair of opposite sides parallel

Parallelogram

Opposite sides parallel, opposite sides congruent

Rhombus

Parallelogram, 4 congruent sides

Rectangle

Parallelogram, 4 right angles

Square

Parallelogram, 4 right angles, 4 congruent sides

Transformation

The movement of a geometric figure

Intersecting Lines

A straight path that has one end point and extends forever in the opposite direction

Congruent figures

Figures that are the same size and same shape

Similar figures

Figures that are the same shape and may or may not have the same size

Line of symmetry

Place where a figure can be folded so that both halves are congruent

Complementary angles

Angles that add up to 90

Supplementary angles

Angles that add up to 180

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