Functional Equations with Causal Operators presents the connection between the equations with causal operators and classical types of functional equations that mathematicians will encounter in the literature. It provides basic theorems of existence and uniqueness of the solution and properties of solutions or families of solutions. This volume describes in detail the fundamentals of linear equations, stability theory and several applications and examples. The book is intended to provide basic theory of functional equations (including functional differential equations) with causal operators. These equations encompass most types of equations, which are used in applied science and engineering: ordinary differential equations, integral equations of the Volterra type, equations with delayed argument and integro-differential equations of the Volterra type.