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Parallel lines and transversals are two important geometry concepts because they result in special angle relationships you’ll find in different postulates and theorems and use for solving geometry proofs.

First, two definitions:

**Parallel lines:** Never intersect, or cross, one another

**Transversal line:** Intersects two or more lines or line segments

When a transversal line crosses a pair of parallel lines, many types of angles can be created. Let’s go over the many different pairs of angles created by parallel lines and transversals: