Ordinary Differential Equations (ODEs) are a type of differential equation that involves a single independent variable and its derivatives with respect to that variable. In other words, ODEs describe the relationships between an unknown function and its derivatives in a single-variable context. These equations are used to model a wide range of phenomena in various scientific and engineering fields.

The general form of a first-order ODE is:

dy/dx = F(x, y)

Here, y is the unknown function of x, and F(x, y) represents a given function that relates y and its first derivative.

Higher-order ODEs involve higher derivatives of the unknown function, and their general form is:

d^n y/dx^n = F(x, y, dy/dx, d^2y/dx^2, ..., d^(n-1)y/dx^(n-1))

In words, these equations describe how the rate of change of a function depends on the function itself and its derivatives.

Solving ODEs typically involves finding the function y(x) that satisfies the given equation. The solution may be an explicit formula for y(x) or a qualitative description of the behavior of y(x).

Applications of ordinary differential equations are widespread and include modeling physical phenomena such as population growth, chemical reactions, electrical circuits, and mechanical systems, among others. The study of ODEs is a fundamental topic in the field of differential equations and plays a key role in understanding dynamic systems.