Describing shapes by attributes means noticing and naming properties like the number of sides, corners (vertices), and whether edges are straight or curved. A triangle has 3 sides and 3 corners; a circle has no corners and no straight sides. These descriptions prepare children for more formal geometric reasoning.
Have children count sides and corners on real shape cutouts. Ask descriptive questions: 'How is a square different from a circle? How is it the same as a rectangle?'
You already know the names of shapes — you can look at a triangle and say "that's a triangle." Describing shapes by their attributes is the next step: instead of just naming a shape, you explain *why* it has that name, using words like "sides" and "corners." Attributes are the things you can count or observe that make one shape different from another.
A side is a straight line segment that makes up part of the shape's border. A corner (sometimes called a vertex) is the pointy place where two sides meet. A triangle has 3 sides and 3 corners — count them by touching each one. A square has 4 sides and 4 corners. A rectangle also has 4 sides and 4 corners, just like a square, which is why we say squares and rectangles are related shapes: they share those attributes. The difference is that a square's 4 sides are all the same length.
A circle is special because it has no straight sides and no corners. Its border is one smooth curve that goes all the way around without any corners or flat parts. This is what makes a circle completely different from a triangle or square. Some children say a circle has "one side," but that's not quite right — a side must be straight. The circle's border is curved the whole way, so we say zero sides.
When you describe a shape, think of it like answering two questions: "How many sides does it have?" and "How many corners does it have?" A shape with 3 of each is a triangle. A shape with 4 of each is a rectangle or square. A shape with 5 of each is a pentagon. These descriptions help you sort, compare, and eventually measure shapes — skills you'll keep using as you learn more math.