1. Plane Figures
3rd Grade
Mrs. Salgado

2. right angle
An angle that forms a square corner Example:                     

3. angle
A figure formed by two rays or line segments that share an endpoint. Example:                       

4. acute angle
An angle that has a measure less than a right angle. Example:                                           

5. obtuse angle
An angle that has a measure greater than a right angle. Example:                                           
                                          

6. polygon A closed plane figure with straight sides that are
line segments. Examples:                                                 
                                          

7. quadrilateral
A polygon with four sides Examples:
                                          

8. equilateral
triangle
A triangle that has three equal sides. Example:                 
                                          

9. Isosceles triangle
 A triangle that has two equal sides. Example:                    
                

10. right triangle
A triangle with one right angle Example:                                
                

11. scalene triangle
A triangle in which no sides are equal Example:                                             
                     

12. line segment
A part of a line that includes two points, called endpoints, and all the points between them. Example:                                             
                     

13. radius
A line segment with one endpoint at the center of a circle and the other endpoint on the circle. Example: