This document defines and provides examples of key terms related to lines and angles in geometry, including parallel lines, skew lines, parallel planes, and different types of angles (corresponding, alternate exterior, alternate interior, consecutive interior) that are formed when a transversal line intersects two coplanar lines. Diagrams are included to illustrate the different types of angles formed with a transversal.

1. Terms of Endearment Lines and Angles: 3.1

2. Parallel Lines Coplanar lines that do not intersect

3. Skew Lines Non-Coplanar lines that do not intersect

4. Parallel Planes Planes that do not intersect

5. Parallel Postulate If there is a line and a point not on the line, then there is exactly one line through the point parallel to the given line

6. Perpendicular Postulate If there is a line and a point not on the line, then there is exactly one line through the given point perpendicular to the given line

7. Transversal A line that intersects two or more coplanar lines at different points Most of what will be referred to as a transversal will deal with parallel lines and the transversal being the line that intersects both of them, but transversals do not have to go through parallel lines only…by definition they simply go through two coplanar lines

8. Corresponding Angles Two angles that occupy corresponding positions in reference to the four angles created at each line by the transversal Angles 1 and 5 are in the upper-left 3 and 7 lower-left 2 and 6 upper-right 4 and 8 lower-right 1 2 3 4 5 6 7 8

9. Alternate Exterior Angles Two angles that lie on the outside the two lines on opposite sides of the transversal Angles 1 and 8 Angles 2 and 7 1 2 3 4 5 6 7 8

10. Alternate Interior Angles Two angles that lie between the two lines on opposite sides of the transversal Angles 3 and 6 Angles 4 and 5 1 2 3 4 5 6 7 8

11. Consecutive Interior Angles These are also referred to by some as Same Side Interior Angles Two angles that lie between the two lines on the same side of the transversal Angles 3 and 5 Angles 4 and 6 1 2 3 4 5 6 7 8