A parabola is a curve that looks like the one on the right. Its open end can point up, down, left or right. A curve of this shape is called 'parabolic', meaning 'like a parabola'.

There are three common ways to define a parabola:

1. Focus and Directrix

In this definition we start with a line (directrix) and a point (focus) and plot the locus of all points equidistant from each. For more see Parabola (focus and directrix).

2. The graph of a function

When we plot the graph of a function of the form the x2 term causes it to be in the shape of a parabola. For more on this see Parabola (Graph of a function).

3. As a conic section

A parabola is formed at the intersection of a plane and a cone when the plane is parallel to one side of the cone.
See Parabola (Conic section).

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