Vector?eldsonmanifoldsplaymajorrolesinmathematicsandothersciences. In particular, the Poincar e Hopf index theorem and its geometric count- part, the Gauss Bonnettheorem, giveriseto the theoryof Chernclasses, key invariants of manifolds in geometry and topology. One has often to face problems where the underlying space is no more a manifold but a singular variety. Thus it is natural to ask what is the good notionofindexofavector?eld, andofChernclasses, ifthespaceacquiress- gularities.Thequestionwasexploredbyseveralauthorswithvariousanswers, starting with the pioneering work of M.-H. Schwartz...