2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/147599A geometric construction of Sullivan's Stiefel-Whitney homology classes of a real analytic variety $X$ is given by means of the conormal cycle of an embedding of $X$ in a smooth variety. We prove that the Stiefel-Whitney classes define additive natural transformations from certain constructible functions to homology. We also show that, for a complex analytic variety, these classes are the mod 2 reductions of the Chern-MacPherson classes.28 pages, AMSTeX Version 2.1, format AMSppt. The only change is that \input amstex \documentstyle{amsppt} has been added to the fileDifferential Geometrytext