## 19 terms · ThinkMath Chapter 9

### polygon

A closed shape with straight lines that do not cross.

### closed shape

A shape that has a perimeter with no openings.

### open shape

A shape that has a perimeter with openings.

### side

A The outside straight line between two vertices.

### vertex

The point where where two sides meet to make an angle or a corner.

### triangle

A polygon with three sides and 3 vertices.

A polygon with four sides and four vertices.

### rectangle

A quadrilateral polygon with opposite sides that are parallel and 4 right angles.

### square

A rectangle with four equal sides and four right angles.

### congruent figures

Figures that are exactly the same in size and shape.

### similar figures

Figures that are the same in shape, but are different in size.

### line of symmetry

A line that divides a figure into two sides that mirror each other.

### cardinal directions

North, South, East, West.

### compass rose

A symbol in a map showing the cardinal directions.

### trapezoid

A quadrilateral polygon with one pair of parallel sides.

### rhombus

A quadrilateral polygon with 2 pairs of parallel lines that is shaped like a diamond.

### pentagon

A polygon with 5 sides and 5 vertices.
Penta means 5

### hexagon

A polygon with 6 sides and 6 vertices.

### octagon

A shape with 8 sides and 8 vertices. Octa means 8.

### Flickr Creative Commons Images

Some images used in this set are licensed under the Creative Commons through Flickr.com. Click to see the original works with their full license.