# What is the directrix of a parabola?

##### 1 Answer

Oct 31, 2015

The *directrix* of the parabola is a straight line that, together with the *focus* (a point), is used in one of the most common definition of parabolas.

In fact, a parabola can be defined as *the locus of points

The directrix has the property of being always perpendicular to the axis of symmetry of the parabola.