Naming shapes by counting sides
A shape’s name comes from how many straight sides it has, so counting is all you need.
Count the sides, not the look
A triangle has three straight sides. That is the whole rule.
It is still a triangle if it is thin, upside down, or leaning over. Shapes do not stop being themselves when you turn them. So put your finger on one corner and count the sides as you go around, rather than deciding by how it looks.
The names follow the numbers
Three sides is a triangle. Four sides with all of them equal is a square, and four sides with two long and two short is a rectangle. Five sides is a pentagon. Six sides is a hexagon.
The names sound harder than they are, and every one of them is just a number in disguise.
Round shapes have no sides at all
A circle has no straight sides and no corners. An oval is the same idea, stretched.
Here is the test: run your finger around the edge. If it never has to turn a sharp corner, the shape is round.
A shape can look odd and still be itself
A triangle does not have to sit flat with a point at the top. It can be long and thin, tipped on its side, or stretched until it looks nothing like the one in the picture book.
If it has three straight sides and is closed all the way round, it is a triangle. That is the whole test.
The same goes for every other name. A very long rectangle is still a rectangle. A square turned on its corner is still a square, even when somebody calls it a diamond.
Corners come in the same number as sides
Count the sides and you already know the corners, because every straight side meets another one at each end.
A triangle has three of each. A pentagon has five of each. If your two counts disagree, you have missed a side or counted one twice — go round the shape again with your finger.
That check is worth doing on any shape with more than four sides, where it is easy to lose your place.
Worked examples
A shape has six straight sides. What is it called?
Six sides is a hexagon. The cells in a honeycomb are hexagons, and so are many floor tiles.
Answer: Hexagon
A triangle is turned upside down. Is it still a triangle?
Turning a shape does not add or remove sides. Count them again after the turn and there are still three. Three sides means triangle, whichever way up it is.
Answer: Yes
Sam says a long thin four-sided shape cannot be a rectangle because it is "too stretched". Is Sam right?
No. A rectangle needs four straight sides and square corners, and nothing says how long they have to be. A door and a ruler are both rectangles.
Answer: No, it is still a rectangle
How many corners does a shape with five straight sides have?
Sides and corners come in pairs: every place two sides meet is a corner. Five sides means five corners. That is true for every straight-sided shape.
Answer: 5
A shape has four straight sides, but it is long and thin. What is it?
Four straight sides makes it a quadrilateral, and if the corners are square it is a rectangle. Being long and thin changes nothing.
Answer: A rectangle
How many corners does an octagon have?
An octagon has eight sides, and corners always match sides, so it has eight corners.
Answer: 8
Is a circle a shape with one side?
Sides are straight. A circle is one curved edge all the way round, so it has no straight sides and no corners at all.
Answer: No — it has no sides
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