A shape’s boundary may consist of straight sides, curved sides, or a combination of both; straight sides are line segments, while curved sides bend continuously rather than forming a segment. This understanding supports describing and classifying familiar two-dimensional shapes, including distinguishing shapes by their boundary features rather than by orientation, size, or color; more formal properties of curves are not included.
Look at the boundary, or outside edge, of the shape. Move your finger around the edge and notice whether each part is straight or bends.
Example: A shape has a bottom side, two upright sides, and a rounded top.
So, the shape has:
Remember: Count the parts of the outside boundary. A shape can have only straight sides, only curved sides, or both.
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