Lesson objective: Understand lines can be classified as parallel and perpendicular.

Students bring prior knowledge of lines and angles from 4.G.A.1. This prior knowledge is extended to identify and draw parallel and perpendicular lines as students classify lines. A conceptual challenge students may encounter is understanding that perpendicular lines may appear as simply intersecting lines depending on the orientation.

The concept is developed through work with concrete examples, supporting concept development before moving on to representational and abstract representations.

This work helps students deepen their understanding of equivalence because parallel lines remain an equal distance apart and perpendicular lines must have four right angles.

Students engage in Mathematical Practice 6 (attend to precision) as they identify and represent parallel and perpendicular lines.

**Key vocabulary:**

- line
- parallel
- perpendicular
- point
- ray