To give a quadrilateral its best name, check three things: equal sides (matching tick marks), parallel sides (matching arrows) and right angles (small squares). Square: 4 equal sides and 4 right angles. Rectangle: 4 right angles, sides not all equal. Rhombus: 4 equal sides, no right angles. Parallelogram: 2 pairs of parallel sides. Trapezium: exactly 1 pair of parallel sides. Kite: 2 pairs of equal sides next to each other. Choose the most exact name that fits. On a dot grid, count the steps along each side: matching steps mean equal sides, and steps in the same direction mean parallel sides.
Explore this idea with maths tools
Maths you can move
Build 8 + 5
Tap two gold counters to fill the ten-frame.
8 in the frame + 5 waiting. The total stays the same.
Words to know
- parallel
- always the same distance apart, never meeting
- rhombus
- a quadrilateral with 4 equal sides
- trapezium
- a quadrilateral with 1 pair of parallel sides
Worked examples
Best name: 4 equal sides and 4 right angles.
- 1.4 right angles make it a rectangle family shape.
- 2.All sides equal as well, so the most exact name is square.
= square
Best name: a tilted shape with 4 equal sides and no right angles.
- 1.4 equal sides: a rhombus family shape.
- 2.No right angles, and tilting does not change the name.
= rhombus
Best name: on a dot grid, one pair of sides both go 2 right and 1 up; the other two sides go different ways.
- 1.Matching steps in the same direction: one pair of parallel sides.
- 2.The other pair is not parallel.
= trapezium
For parents
Method: Check sides, then parallel pairs, then corners, and give the most exact name.
What to say: Which sides match? Which are parallel? Are the corners square? What is the most exact name?
Common mistakes:
- Checks only the angles, so a square (four right angles) is named 'rectangle' and its equal sides are ignored.
- Checks only the sides, so a square (four equal sides) is named 'rhombus' and its right angles are ignored.
- Gives a true but more general family name (parallelogram for a rectangle, quadrilateral for a kite) instead of the best, most exact name.
- Judges corners by eye and treats slanted corners as right angles, naming a rhombus a square or a parallelogram a rectangle.
- Assumes the sides are all equal without checking, naming a rectangle a square or a parallelogram or kite a rhombus.
- Names a shape standing on a corner by its look ('diamond') instead of its properties.
- Calls a shape with one pair of parallel sides a parallelogram, not knowing a parallelogram needs two pairs.