Hi Kiara.

The name we usually use for a 13-sided polygon is "triskaidecagon".
There is a Wikipedia entry on it here. However, another excellent (but rather advanced) math site called Math World prefers the term "tridecagon". That's rather less well-known in my experience.

By the way, there are quite a few other names for many-sided polygons at the Math World link. Did you know, for example, that a 10,000-sided figure is a "myriagon"? We also have a list of names for polygons but ours only goes up to 20 sides.

Now here's a question for you: what three-dimensional figure, that you can make with paper, scissors and a bit of tape, has only one side and only one edge?

Stephen La Rocque.>