Lesson objective: Explore the characteristics that define different shapes and the names of those shapes.

Students bring prior knowledge of naming shapes regardless of their orientations or overall size from (K.G.2). This prior knowledge is extended to defining and non-defining attributes as students determine what things are true for all triangles, all squares, etc. A conceptual challenge students may encounter is thinking attributes such as size, color, and orientation are what determine a shape.

The concept is developed through a sorting activity, which encourage students to consider common attributes and predict which shape can be added to a circle based on a defining attribute.

This work helps students deepen their understanding of numbers because shapes can be defined by number of sides, angles, and faces.

Students engage in Mathematical Practice 3 (Construct viable arguments and critique the reasoning of others) as they use clear definitions with peers and define attributes and provide a viable argument reasoning why a shape lacks specific attributes.

**Key vocabulary:**

- angle
- attribute
- defining
- non-defining

**Materials: (optional)**

- attribute blocks
- geoboards (and rubberbands)