Learn the Method
1Count the straight sides.
Every corner (vertex) joins exactly two sides — sides and vertices always match.
2Use the Greek prefix.
Penta = 5, hexa = 6, hepta = 7, octa = 8 — like an octopus's 8 legs.
32D means flat.
2D shapes have length and width but no thickness — drawings, not objects.
Worked Example
Name each shape.
Watch Out! Common Mistakes
Careful! Tick each side as you count round — sides = vertices, so a shape with 6 corners has exactly 6 sides.
Wrong! Polygons need straight sides. A circle is a 2D shape but not a polygon.
Wrong! A square turned 45° is still a square (not a “diamond”) — names depend on sides and angles, not which way up it sits.
⬇ Cheat Sheet
- Count the straight sides.
- tri 3 · quad 4 · penta 5 · hexa 6 · hepta 7 · octa 8
- Sides = vertices, always.
- A rotated shape keeps its name.
📖 Continue Your Journey
Quick summary
- 2D shapes are flat; polygons have straight sides that close up.
- Count sides to name: tri 3, quad 4, penta 5, hexa 6, hepta 7, octa 8.
- Sides and vertices always match in number.
- Rotating a shape never changes its name.
Frequently asked questions
What is a polygon?
A flat (2D) shape made of straight sides that join up with no gaps. Triangles, squares and hexagons are polygons; circles are not, because their side is curved.
How do children remember shape names?
Through the prefixes: penta (5), hexa (6), hepta (7), octa (8) — anchored to words like pentathlon and octopus.
Is a tilted square a diamond?
No — it's still a square. Shape names depend on sides and angles, not orientation. 'Diamond' isn't a mathematical shape name.
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