Lesson objective: Understand that area is an attribute of plane figures describing how much two-dimensional space is covered by the figure.

Students bring prior knowledge that shapes have both defining (number of sides) and non-defining (color, overall size) attributes from 1.G.1. This prior knowledge is extended to include area as a way to measure and describe plane figures as students come to understand the need for a way to measure the total space covered by a plane figure. A conceptual challenge students may encounter is the difference between measuring length and area.

The concept is developed through work with a variety of plane figures, which supports the idea that all plane figures have area that can be measured.

This work helps students deepen their understanding of number because finding the area is a way to measure and describe the size of a plane figure.

Students engage in Mathematical Practice 2 (reason abstractly and quantitatively) as they think about the properties of the different items in the backyard. They will reason about which properties are relevant to determining the size of each item.

**Key vocabulary:**

- area
- attribute
- length
- measure
- plane figure
- size
- two-dimensional space
- width