a mathematical model that describes how something is changing (or something's rate of change, hence it involves a derivative)

an algebraic relation between variables that includes the rates of change of the variables as well as their instantaneous values

an equation for an unknown function, say y ( x ), which involves derivatives of the function

an equation involving an unknown function and its derivatives

an equation involving an unknown function of one or more variables , its derivatives and the independent variables

an equation relating a function y , its derivative y ' , and the independent variable t

an equation that consists of an unknown function and its derivatives

an equation that involves at least one derivative

an equation that involves the derivative of an unknown function

a relationship between a function and its derivatives

a relationship between a function, in our case S , and the derivatives of the function

Equation which includes one or more derivatives of a variable, and which has to be solved with special methods.

An equation with one or more derivatives in it. (,,','',''',...)[ edit] [ edit

In mathematics, a differential equation is an equation which involves the derivatives of an unknown function represented by a dependent variable. Many of the fundamental laws of physics, chemistry, biology and economics can be formulated as differential equations. They express the relationship involving the rates of change of continuously changing quantities modeled by functions and are used whenever a rate of change (derivative) is known but the process originating is not.