On families of singular plane projective curves

Summary In this article it is studied, in modern form, the classical concept of «complete continuous system of projective plane curves of degree n, with singularities of a certain type». Properties of these schemes are studied (universal properties, techniques to compute tangent spaces, smoothness, special points, etc.). As an application, a modern presentation of the classical theories of systems of curves with nodes, and with nodes and cusps, is given.