** Lesson's Content **

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** Lesson's Glossary **

**Angle
Geometry shape formed by two rays (initial and ending sides of the angle) that share a common endpoint called the vertex. You may name an angle using the vertex, or a point in each ray and the vertex label in the center. **

**Concave polygon
If a polygon has diagonals that lie outside the polygon then the polygon is concave.**

Convex polygon

A convex polygon is any polygon that is not concave.

**Decagon
A ten-sided polygon. **

**Dodecagon
A twelve-sided polygon. **

**Heptagon
A seven-sided polygon.
Hexagon
A six-sided polygon.
irregular polygon
An irregular polygon is any polygon that is not regular. **

**N-gon
A polygon with n sides. **

**Nonagon
A nine-sided polygon. **

**Octagon
An eight-sided polygon. **

**Pentadecagon
A 15-sided polygon.
Pentagon
A five-sided polygon. **

** Polygon
A polygon is a two-dimensional geometric figure with these characteristics: •
It is made of straight line segments.
Each segment touches exactly two other segments, one at each of its endpoints.
It is closed -- it divides the plane into two distinct regions, one inside and the other outside the polygon.
Regular polygon
A regular polygon has sides that are all the same length and angles that are all the same size.**

**Quadrilateral
A four-sided polygon.**

**Septagon
A seven-sided polygon. **

**Side of a polygon
- a single segment from the union that forms a polygon. **

**Vertex of a polygon
An endpoint of a segment in a polygon.**

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