An ordered vector basis for a finite-dimensional vector
space
defines an orientation. Another basis
gives the same orientation if the matrix
has a positive determinant, in which case the basis
is called oriented.
Any vector space has two possible orientations since the determinant of an nonsingular
matrix is either positive or negative. For example, in ,
is one orientation and
is the other orientation. In three
dimensions, the cross product uses the right-hand
rule by convention, reflecting the use of the canonical orientation
as
.
An orientation can be given by a nonzero element in the top exterior power of ,
i.e.,
.
For example,
gives the canonical orientation on
and
gives the other orientation.
Some special vector space structures imply an orientation. For example, if is a symplectic form
on
,
of dimension
,
then
gives an orientation. Also, if
is a complex vector space,
then as a real vector space of dimension
, the complex structure
gives an orientation.