The QFocus
Trapezium » Trapezoid » Parallelogram
1. The arrows show a progression from a Trapezium (a quadrilateral with zero pairs of parallel sides), to a Trapezoid (a quadrilateral with one pair of parallel sides), to a parallelogram (a quadrilateral with two pairs of parallel sides). I thought by isolating this attribute in this way, I could help kids start to see a shape like a parallelogram as a figure with a set of attributes, rather than a shape that looks long and slanted.
2. I was pretty sure that there would be fifth graders who would know what a trapezoid was, and it was also a safe bet that parallelogram wouldn’t be a foreign term for some of them either. However, I was equally confident that no one would have a clue what a Trapezium was so between that and the arrows, there should be something unknown for everyone to ask questions about.
- Is a trapezium a 3D figure?
- How many faces, edges, and vertices are in a trapezoid?
- Who made up a parallelogram?
- Does a parallelogram and a trapezoid have the same amount of sides?
- What do the arrows mean?
- What are the attributes for a trapezoid?
- Why do trapezium and trapezoid have the same first 6 letters?
- Does the pronunciation of the words effect the relationship?
- What does a parallelogram look like?
- What do trapeziums, trapezoids, and parallelograms have in common?
The Etymology of the words Trapezoid and Trapezium
I looked it up after I saw the students’ question and realized that there are several etymological issues related to the words Trapezoid and Trapezium. First, those words have a different meaning in Europe than the United States. What we commonly refer to as a trapezoid in The US and Canada is referred to as a Trapezium in English speaking countries outside of North America. Secondly, there is a mathematical disagreement as to whether a Trapezoid has exactly one set of parallel sides (the exclusive definition) or at least one set of parallel sides, which would make a parallelogram a special kind of trapezoid (that puppy is starting to look more and more like a tomato!). Apparently, the second definition is more useful in higher mathematics courses like Calculus, which is interesting because I have always taught the first. These words both originated from a Greek word meaning ‘little table.’