# Consecutive Interior Angles

When two lines are crossed by another line (called the Transversal):

The **pairs of angles** on one side of the transversal but inside the two lines are called **Consecutive Interior Angles**.

In this example d and f are Consecutive Interior Angles

Also c and e are Consecutive Interior Angles

To help you remember: the angle pairs are **Consecutive** (they follow each other), and they are on the **Interior** of the two crossed lines.

## Parallel Lines

When the two lines being crossed are Parallel Lines the **Consecutive Interior Angles add up to 180°**.

images/parallel-pair.js

*(Click on "Consecutive Interior Angles" to have them highlighted for you.)*

Language Note: Also called **Co-Interior Angles** in the UK and Australia

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