Understanding Two-Dimensional Shapes

Two-dimensional shapes, often called 2D shapes, are completely flat. You can draw them on a piece of paper. To understand, describe, and name these shapes, we look closely at their sides and corners.

Parts of a 2D Shape

When we describe a flat shape, we usually count two things:

• Sides: The straight lines that make up the outside edge of the shape.
• Corners (Vertices): The pointy parts where two sides meet.

Common 2D Shapes

Let's look at some flat shapes you will see every day:

• Circle: A circle is perfectly round. It has $0$ straight sides and $0$ corners.
• Triangle: A triangle has $3$ sides and $3$ corners. A slice of pizza or a yield sign on the road is shaped like a triangle!
• Square: A square has $4$ sides and $4$ corners. The special thing about a square is that all $4$ sides are exactly the same length.
• Rectangle: A rectangle also has $4$ sides and $4$ corners, but its sides are not all the same length. It has $2$ long sides and $2$ short sides. Think of a door, a TV screen, or a book.
• Hexagon: A hexagon is a larger shape that has $6$ sides and $6$ corners. A honeycomb cell made by bees is a perfect hexagon.

Practice Examples

Here are some common questions to help you practice identifying shapes:

1. How many sides does a triangle have? Look at the prefix "tri-" (which means three). A triangle always has exactly $3$ sides and $3$ corners.

2. Name the shape with 6 sides. A shape with exactly $6$ straight sides is called a hexagon.

3. Is this a square or a rectangle? To tell the difference, look at the length of the sides. Both have $4$ sides and $4$ corners. However, if all $4$ sides are the exact same length, it is a square. If two sides are long and two sides are short, it is a rectangle.