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Sort 2D Shapes by Attribute

This lesson explains how to sort two-dimensional shapes by attributes, including the number of sides, the number of corners, whether sides are straight or curved, and size. Students practice grouping shapes like triangles, squares, rectangles, and circles into clear categories.

What Does It Mean to Sort 2D Shapes by Attribute?

An attribute is simply a feature or property that a shape has. When we sort 2D shapes by attribute, we look closely at a group of flat shapes and decide how to organize them based on something they share, such as the number of sides, the number of corners, the type of edges, or the size of the shape. Sorting helps us notice what makes shapes alike and what makes them different, which is an important step before learning how shapes can be broken apart and put back together in a lesson like composing and decomposing 2D shapes.

Common Attributes Used to Sort 2D Shapes

Before sorting a set of shapes, it helps to know which attributes to look for. Here are the most common ones used with flat shapes:

Number of sides: A triangle has 3 sides, a square or rectangle has 4 sides, a pentagon has 5 sides, and a hexagon has 6 sides.
Number of corners (vertices): The point where two sides meet is called a corner. Shapes with more sides usually have more corners.
Type of sides: Some shapes are made only of straight sides, while others, like circles and ovals, have curved sides.
Size: Shapes with the same name, like two squares, can still be sorted by whether they are bigger or smaller.

How to Sort Shapes Step by Step

Sorting a group of shapes is easier when you follow the same steps every time.

Look at the whole set of shapes and choose one attribute to sort by, for example the number of sides.
Check each shape one at a time and count that attribute.
Place shapes with the same result into the same group.
Once every shape has a group, check your work by making sure each shape truly matches the label of its group.

Example: Sorting Shapes by Number of Sides

Imagine you are given a triangle, a square, a rectangle, a pentagon, and a hexagon. If the attribute is the number of sides, you would sort them into three groups: shapes with 3 sides, shapes with 4 sides, and shapes with 5 or more sides.

The triangle goes in the 3-sides group, the square and rectangle go in the 4-sides group, and the pentagon and hexagon go in the 5-or-more-sides group.

Example: Sorting Shapes by Straight or Curved Sides

Another common attribute is whether a shape has only straight sides or at least one curved side. A triangle and a square are made entirely of straight sides, but a circle has one curved side and no corners at all.

The triangle and rectangle belong with shapes that have only straight sides, while the circle and oval belong with shapes that have a curved side.

Sorting by Size

Shapes can also be sorted even when they share the same name and the same number of sides. For example, if you are given several squares of different sizes, you can sort them into a group of smaller squares and a group of larger squares. This kind of sorting reminds us that the name of a shape does not tell us everything about it, size is its own attribute and should be checked separately from the number of sides or corners.

Why Sorting Shapes by Attribute Matters

Sorting builds the habit of looking carefully at a shape's properties instead of just its overall appearance. This same skill of noticing sides, corners, and edges is useful later when you learn to identify 2D shapes hiding inside 3D shapes, since recognizing a flat shape's attributes helps you spot it as the face of a solid figure. Practicing with different shape sets, whether on paper or with a hands-on shape game, makes it easier to sort quickly and correctly every time.

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