What is an orthogonal vector?

An orthogonal vector is a vector that is at an angle of 90 degrees, or perpendicular, to another vector. Up to three vectors can be mutually orthogonal to each other in a three-dimensional space.

To check if two vectors are orthogonal, take their dot product. If the dot product of two vectors is equal to zero, then they are orthogonal to each other. Alternatively, taking the cross product of two vectors always yields a third vector that is orthogonal to the first two. This is always true unless that cross product is equal to zero, in which case the first two vectors do not intersect and are parallel instead.