F. Lizzi, G. Marmo, G. Sparano (Napoli) and A. M. Vinogradov (Salerno) EIKONAL TYPE EQUATIONS FOR GEOMETRICAL SINGULARITIES OF SOLUTIONS IN FIELD THEORY (52K, LaTeX) ABSTRACT. We discuss several aspects of singularities of the solutions of the partial differential equations of Klein--Gordon, Schr\"odinger and Dirac. In particular we analyze the fold type singularity, of the first and higher orders, and the related characteristic equations. We also consider the field equations as reduction of homogenous equations in higher dimensions, and discuss how singularities of the solution are reduced.