DIFFERENTIAL EQUATIONS

From our MAM246W course notes a differential equaition is defined as an equation contatining a derivative of an unkown function. 
For Example
If population growth rate of a species of animals is proportional to the number of animals at the momemnt. Then growth rate can be modelled by the following differential equation:
dy/dt=ky(t).
          where

• t is the independent variable (time)
• y is the dependent variable (number of animals)
• k is the parameter

dy/dt=ky(t) is a differential equation as it contains the function y(t) and its derivative dy/dt.