Triangles and quadrilaterals
- Equilateral triangle: 3 equal sides and three 60° angles. Isosceles: 2 equal sides and 2 equal angles. Scalene: no equal sides. Right-angled: one 90° angle.
- Square and rectangle: four right angles. Rhombus: four equal sides, opposite angles equal. Parallelogram: opposite sides parallel and equal. Trapezium: one pair of parallel sides. Kite: two pairs of equal sides next to each other.
Polygons, symmetry and circles
- Polygons: pentagon (5 sides), hexagon (6), heptagon (7), octagon (8), decagon (10). A regular polygon has all sides and all angles equal.
- Line symmetry: a square has 4 lines of symmetry. Rotational symmetry: the order is how many times the shape fits onto itself in one turn (a square has order 4; a rectangle has order 2).
- Parts of a circle: radius, diameter (twice the radius), circumference, chord, tangent (touches the circle at one point), arc, sector and segment.
3D shapes
- Faces, edges and vertices: a cube has 6 faces, 12 edges and 8 vertices. A triangular prism has 5 faces, 9 edges and 6 vertices. A square-based pyramid has 5 faces, 8 edges and 5 vertices.
- A cylinder has 2 flat circular faces and 1 curved face. A cone has 1 flat face and a point.
- A net is a flat shape that folds up to make a 3D shape. Plans and elevations are views from above, the front and the side.
- Congruent shapes are identical in shape and size. Similar shapes are the same shape but a different size.
Key terms
- Polygon
- A 2D shape with straight sides.
- Regular polygon
- A polygon with all sides and all angles equal.
- Quadrilateral
- A polygon with four sides.
- Line of symmetry
- A line that divides a shape into two mirror images.
- Rotational symmetry
- When a shape looks the same after less than a full turn.
- Radius
- The distance from the centre of a circle to its edge.
- Diameter
- The distance across a circle through its centre (twice the radius).
- Tangent
- A straight line that touches a circle at one point.
- Face
- A flat or curved surface of a 3D shape.
- Edge
- Where two faces of a 3D shape meet.
- Vertex
- A corner of a shape (plural: vertices).
- Net
- A flat shape that folds up to make a 3D shape.
- Congruent
- Exactly the same shape and size.
- Similar
- The same shape but a different size.