What is higher order infinitesimal? How to apply it in finding limit? Give an example

What is higher order infinitesimal? How to apply it in finding limit? Give an example


For example, 1 / n tends to be infinitesimal when n →∞
And 1 / N ^ 2 tends to be infinitesimal when n →∞
But 1 / N ^ 2 is much smaller than 1 / n
So 1 / N ^ 2 is infinitesimal of higher order than 1 / n
The main application in limit is that higher order infinitesimal can be obtained in molecule, and the result is 0