The *right hand rule* is a rule to determine the sense of a vector perpendicular to two vectors A and B. If you curl the fingers of the right hand in the direction from A to B along the smaller angle between A and B than the direction of C is pointing in the direction of your extended thumb or the direction in which a right-hand screw would move. If the direction of the movement from A to B is *counterclockwise* this direction is out of the plane formed by A and B and otherwise into the plane.

More general any ordered triple of vectors $(\vec u, \vec v, \vec w)$ with a common origin in $\mathbb{R}^3$ is a *right-handed triple* if the vectors are not in the same plane and the shortest turn from $\vec u$ to $\vec v$ as seen from the tip of $\vec w$ is *counterclockwise* otherwise the triple is a *left-handed triple*.

A three-dimensional *coordinate system* in which the vectors formed by the positive axes satisfy the right-hand rule is called a *right-handed coordinate system*, while one that does not is called a *left-handed coordinate system*.