Parallel and perpendicular lines
Identify horizontal and vertical lines and pairs of perpendicular and parallel lines
What a learner can do afterwards
- Point out horizontal and vertical lines in shapes and real-world contexts
- Identify a pair of parallel lines (lines that never meet and are always the same distance apart)
- Identify perpendicular lines (lines that meet at a right angle)
The lesson
Look around you. Some lines lie flat, like the edge of a table. We call these horizontal lines. Other lines stand up tall, like a flagpole or a doorframe. We call these vertical lines.
Sometimes two lines cross and make a right angle, like a square corner. You already know a right angle. When two lines meet like that, we call them perpendicular lines.
Mia watches a train go by. She notices the two rails of the track run side by side. They never touch and always stay the same distance apart. Mia knows these rails are parallel lines.
Here is a quick way to check: if two lines make a right-angle corner, they are perpendicular. If two lines run side by side and never get closer or farther apart, they are parallel.
Perpendicular lines cross at a right angle; parallel lines run side by side and never meet.
Watch it
Where it sits
Learn first
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.