# Overview of Ordinary Differential Equations (ODEs)

There are four major areas in the study of ordinary differential equations that are of interest in pure and applied science.

• Exact solutions, which are closed-form or implicit analytical expressions that satisfy the given problem.
• Numerical solutions, which are available for a wider class of problems, but are typically only valid over a limited range of the independent variables.
• Qualitative theory, which is concerned with the global properties of solutions and is particularly important in the modern approach to dynamical systems.
• Existence and uniqueness theorems, which guarantee that there are solutions with certain desirable properties provided a set of conditions is fulfilled by the differential equation.

Of these four areas, the study of exact solutions has the longest history, dating back to the period just after the discovery of calculus by Sir Isaac Newton and Gottfried Wilhelm von Leibniz. The following table introduces the types of equations that can be solved by DSolve.

 name of equation general form date of discovery mathematician separable 1691 G. Leibniz homogeneous 1691 G. Leibniz linear first-order ODE 1694 G. Leibniz Bernoulli 1695 James Bernoulli Riccati 1724 Count Riccati exact first-order ODE with 1734 L. Euler Clairaut 1734 A-C. Clairaut linear with constant coefficients with constant 1743 L. Euler hypergeometric 1769 L. Euler Legendre 1785 M. Legendre Bessel 1824 F. Bessel Mathieu 1868 E. Mathieu Abel 1834 N. H. Abel Chini 1924 M. Chini

Examples of ODEs belonging to each of these types are given in other tutorials (clicking a link in the table will bring up the relevant examples).