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Geometrical Terms
Key Vocabulary
Point: A location with no size or dimension
Vertex: A corner or point where lines meet
Line: A straight path extending in both directions
Parallel lines: Lines that never meet, always the same distance apart
Perpendicular lines: Lines that intersect at 90°
Bearing: Direction measured clockwise from north (000° to 360°)
Right angle: Exactly 90°
Acute angle: Less than 90°
Obtuse angle: Between 90° and 180°
Reflex angle: Greater than 180°
Interior angle: Inside a polygon
Exterior angle: Outside a polygon
Similar shapes: Same shape, different size (equal angles, proportional sides)
Congruent shapes: Same shape and size
Scale factor: Ratio used to enlarge or reduce a shape
Types of Shapes
Triangles
Any shape with 3 sides
Equilateral: All sides and angles equal
Isosceles: Two sides and two angles equal
Scalene: All sides and angles different
Right-angled: One angle is 90°
Quadrilaterals
Any shape with 4 sides
Square: All sides equal, all angles 90°
Rectangle: Opposite sides equal, all angles 90°
Kite: Two pairs of adjacent sides equal
Rhombus: All sides equal, opposite angles equal
Parallelogram: Opposite sides parallel and equal
Trapezium: One pair of parallel sides
Polygons
Any 2D shape made up of straight lines. They can be either:
Regular polygon: All sides and angles equal
Irregular polygon: Unequal sides or angles
Common types:
Pentagon (5 sides)
Hexagon (6 sides)
Octagon (8 sides)
Decagon (10 sides)
Circles:
Circle Vocabulary
Centre: Middle point of the circle
Radius: Distance from the center to the edge
Diameter: Distance across the circle through the center. It's 2x the radius
Circumference: Perimeter of the circle
Semicircle: Half of a circle
Chord: Line joining two points on the circle
Tangent: Line touching the circle at one point
Arc: Part of the circumference
Sector: “Pizza slice” portion of a circle (2 radii + an arc)
Segment: Area between a chord and arc
Major arc: angle > 180 from the center and it's the longer path from the 2 points
Minor arc: angle < 180 from the center and it's the shorter path from the 2 points
Solids and Nets
Simple Solids
Cube: 6 square faces with equal sides e.g. dice
Cuboid (rectangular prism): it's like a cube but with unequal sides e.g. shoebox
Prism: 2 congruent bases + rectangular sides
Cylinder: 2 circular faces and a curved surface
Pyramid: 1 base + triangular sides
Cone: 1 circular base + 1 curved surface
Sphere: 1 curved surface, perfectly round
Surface Features
Face: Flat surface
Edge: Line where two faces meet
Vertex: Corner point
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