The rule which determines the orientation of the cross product 
.
The right-hand rule states that the orientation of the vectors' cross product is
determined by placing 
and 
tail-to-tail, flattening the right hand, extending it in the direction of 
, and then curling the fingers in the direction that the angle
makes with 
. The thumb then points in the direction of 
.
A three-dimensional coordinate system in which the 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.
