A differential equation involving derivatives of the dependent variable with respect
to only one independent variable is called an ordinary differential equation, e g ,
3
2
2 d y2
dy
dx
dx
⎛
⎞
+ ⎜
⎟
⎝
⎠
 = 0  is an ordinary differential equation (5)
Of course, there are differential equations involving derivatives with respect to
more than one independent variables, called partial differential equations but at this
stage we shall confine ourselves to the study of ordinary differential equations only