Triangular means having the shape of a triangle: three straight sides and three corners. A slice of pizza is triangular, as is a yield sign on the road, or the sails on many sailboats. The pyramids of Egypt have triangular faces.

The word can describe flat shapes, like a triangular piece of paper you fold in origami, or solid objects, like a triangular prism in math class. Some sandwiches are cut into triangular halves, and tortilla chips are usually triangular. In music, the instrument called a triangle is a thin metal bar bent into a triangular shape that rings when you strike it.

You might also hear triangular used to describe relationships between three people or things. If three friends each have different opinions about where to eat lunch, you could call it a triangular debate. The word suggests that three separate points or parties are involved, just like the three corners of a triangle.

Triangles show up everywhere because they're incredibly strong: a triangular frame won't collapse easily, which is why you see triangular supports in bridges, buildings, and even bicycle frames.