Illustrated definition of Geometry: The branch of mathematics that deals with points, lines, shapes and space. Plane Geometry is about flat...

Geometry is all about shapes and their properties. If you like playing with objects, or like drawing, then geometry is for you!

Easy-to-understand definitions, with illustrations and links to further reading. Browse the definitions using the letters below, or use Search above.

An angle measures the amount of turn. Try It Yourself: This diagram might make it easier to remember: Also: Acute, Obtuse and Reflex are in...

A vertex is a corner. An edge is a line segment between faces. A face is a single flat surface. Let us look more closely at each of those:

A polygon is a flat 2-dimensional (2D) shape made of straight lines. The sides connect to form a closed shape. There are no gaps or curves.

Illustrated definition of Slope: How steep a line is. In this example the slope is 3/5 = 0.6 Also called gradient....

When two lines are crossed by another line (called the Transversal): The angles in matching corners are called Corresponding Angles.

Illustrated definition of Vertex: A point where two or more line segments or edges meet. A corner. Examples: any corner of a pentagon (a...

When parallel lines are crossed by a transversal many angles are the same, as in this example: See Parallel Lines and Pairs of Angles to learn more.