Differential geometry MOC Oriented manifold Let be a -manifold. An atlas is called oriented iff all transition maps have positive Jacobian determinant. An orientation on is the choice of a maximal oriented atlas. #m/def/geo/diff If an orientation exists we say that is orientable. If is semi-Riemannian, we can use orientation to define a Riemannian volume form as well as the Hodge star. Properties A manifold is orientable iff there exists a nonvanishing volume form See also Oriented vector space #state/develop | #lang/en | #SemBr