Lesson objective: Create categories for sets of two-dimensional figures.

This lesson helps to build fluency with classifying two-dimensional figures. Quadrilaterals are used here because they support student awareness of shared attributes. This work develops students' understanding that objects have geometric properties that allow us to create categories of objects.

Students engage in Mathematical Practice 7 (look for and make use of structure) as they use and create organized structures for categories of shapes, to visualize the relationships between different plane figures.

**Key vocabulary:**

- congruent
- geometric
- parallel
- perpendicular
- quadrilateral
- trapezoid