What are dihedral angles?

Dihedral angles are the angles between two flat surfaces that meet at a line, like when you open a book or fold a piece of paper.

Imagine you have a book, and you open it up just a little bit. The two pages form an angle where they meet along the spine. That angle is a dihedral angle! It’s the space between the two flat parts (the pages) that come together at a line (the spine).

Now think about folding a piece of paper in half. When you fold it, you're creating a dihedral angle between the folded part and the open part. If you make a bigger fold, the angle gets bigger, like when you open the book wider.

You can also see dihedral angles in real life: when you lift your arms up to show off a superhero pose, or when two walls of a room meet at a corner. The angle between them is a dihedral angle, just like the one between the pages of a book.