2. adjacent angles

3. alternate exterior angles transversal interior (inside) exterior (outside) Alternate exterior angles are congruent!

4. alternate interior angles exterior (outside) interior (inside) transversal Alternate interior angles are congruent!

5. coincidental lines Example There are actually two lines here, but since their equations are the same, they form the same line, hence overlapping at every point and making it look like there is only one line.

6. congruent angles Example These are congruent angles, because they both measure 50 degrees. 50

7. congruent figures Congruent figures are two or more figures that have congruent corresponding sides and congruent corresponding angles. Example

8. coplanar lines Coplanar lines are two or more lines that lie in the same plane. Example coplanar coplanar NOT coplanar (same plane) (same plane) (different planes)

9. corresponding angles Corresponding angles are angles that have the same relative positions. Example 1 Example 2 A CD B BA DC The matching letters in the figure above are corresponding angles. Corresponding angles are congruent!

10. corresponding sides

11. intersecting lines

12. linear pair of angles (straight line)

13. parallel lines

14. perpendicular lines

15. same-side exterior angles transversal exterior (outside) interior (inside) exterior (outside) Same-side exterior angles equal 180 degrees!

16. same-side interior angles exterior (outside) transversal interior (inside) Same-side interior angles equal 180 degrees!

17. skew lines Example 1Example 2

18. supplementary angles Example 1Example 2 60 120 (a straight line). Supplementary angles equal 180 degrees!

19. transversal

20. vertical angles Vertical angles are congruent!