Glossary — Geometry

Adjacent — next to another side or angle, with a shared boundary.

Angle of depression — the angle between a horizontal line and a line of sight below it.

Angle of elevation — the angle between a horizontal line and a line of sight above it.

Arc — part of a circle's circumference.

Bearing — a direction measured clockwise from north and written as a three-digit angle.

Chord — a straight line joining two points on a circle.

Congruent — having the same shape and size, so matching sides and angles are equal.

Cyclic quadrilateral — a four-sided shape whose vertices all lie on a circle.

Diameter — a straight line through a circle's centre joining two points on its circumference.

Enlargement — a transformation that changes a shape's size using a centre and scale factor.

Face — a flat surface of a three-dimensional shape.

Hypotenuse — the longest side of a right-angled triangle, opposite the right angle.

Locus — the set of points that follow a stated rule.

Midpoint — the point exactly halfway along a line segment.

Perpendicular — meeting at a right angle.

Polygon — a closed, flat shape made from straight line segments.

Prism — a three-dimensional shape with matching parallel ends and a constant cross-section.

Radius — a line from the centre of a circle to its circumference.

Regular polygon — a polygon with all sides equal and all angles equal.

Reflection symmetry — a shape property where a line divides the shape into two matching mirror images.

Sector — the part of a circle enclosed by two radii and an arc.

Segment — the part of a circle enclosed by a chord and an arc.

Similar shapes — shapes with equal matching angles and proportional matching lengths.

Tangent — a straight line that touches a circle at one point.

Transformation — a change in a shape's position, orientation or size.

Vertex — a corner where two or more edges meet.