- Definition
A diagonal is a straight line that connects two corners of a shape, but not corners that are already connected by one of the shape's sides.
Drawing a line from the top-left corner to the bottom-right corner of a square piece of paper creates a diagonal.
How to teach this in 30 seconds
Try this analogy: A diagonal line is like cutting a square sandwich from one corner to the opposite corner.
Ask your child: Can you trace a line from one corner of this square to the opposite corner?
Common mix-up: Kids might think any slanted line is a diagonal. A true diagonal line goes from one corner to an opposite corner inside a shape like a square.
Examples
- The crease made when you fold a square piece of paper from corner to corner.
- Stripes in a drawing that stretch from a top corner to an opposite bottom corner.
diagonal is a term used in Ontario’s Kindergarten to Grade 8 curriculum.
Where this shows up
The descriptions on this page are SmartStudy’s own original, plain-language writing — not the Ministry’s wording. They are aligned to the Ontario Curriculum, © King’s Printer for Ontario. For the Ministry’s official wording, see the source link below. SmartStudy is an independent service and is not affiliated with, endorsed by, or sponsored by the Government of Ontario or the Ministry of Education. Ontario Curriculum and Resources ↗
