In earlier grades, students examined, described, compared, and contrasted attributes of two-dimensional figures. They may have used geometric terms, such as point, line, and segment, intuitively and informally.

This lesson serves two goals. The first is to elicit the language students have for talking about geometric figures, motivating a need to develop more precision in using geometric terminology (MP6). The second is to enable students to see that a line segment is a part of a line, so it has a start point and an endpoint. The Cool-down for this lesson is designed to determine the types of words students use to describe figures. Students may choose to use informal or formal language.

In the next lesson, students will encounter the formal definitions of these geometric terms, but for now, the aim is simply to engage them in noticing and drawing these geometric figures. It is not necessary to expect students to distinguish between line segments and lines in this lesson.

This is the first time students have formally encountered geometry in grade 4. What vocabulary did students bring to the lesson? How might you use their informal language to make formal connections in the next lesson?