**Lesson objective: **Students will understand that shapes have names based on their defining attributes.

Students bring prior knowledge of informally describing the shapes of objects and the relative position of objects from K.G.A.1 in Unit 3. This prior knowledge is extended to formally describing the defining attributes of shapes as students use spatial reasoning skills in geometry. A conceptual challenge students may encounter is understanding that shapes are named based on defining attributes and not by color or size. Another challenge students may encounter is applying the vocabulary to describe shapes.

The concept is developed through work with images of circles, squares, and triangles, which label names of shapes and their defining attributes of sides and corners.

This work helps students deepen their understanding of numbers because students need to count the number of sides and corners of shapes in order to name and identify the shape.

Students engage in Mathematical Practice 2 (Reason abstractly and quantitatively) and Mathematical Practice 7 (Look for and make use of structure) as they use spatial reasoning skills to visualize the defining attributes to identify, describe, and create a shape. They look closely at attributes and use structure to describe shapes.

**Key vocabulary:**

- attributes
- circle
- corners
- sides
- square
- triangle

**Special materials needed:**

- circle, square, and triangle shape cards
- exit ticket shape cards
- solid colored bag

**Prior Knowledge Connection Suggestion: **Display a collection of real marbles of different colors and different sizes. Have students sort the marbles and ask students to explain how they sorted the marbles.

**Exit Ticket Materials:**

- Solid colored bag
- Circle, triangle, and square shape manipulatives or paper shapes.

**Exit Ticket Procedure:** Put the circle, triangle and square shapes into the bag. Have students pull out one shape. Students will name the shape and describe it using its attributes.