What's an example of an infinitesimal? If you want to use infinitesimals to teach calculus, what kind of example of an infinitesimal can you give to the students? What I am asking for are specific techniques for explaining infinitesimals to students, geometrically, algebraically, or analytically.
Note 1. This page is related as is this.

An infinitesimal is some quantity that is explicitly nonzero and yet smaller in absolute value than any real quantity ( http://mathworld.wolfram.com/Infinitesimal.html )
Consider a quantity$=1\:$ for example. Then, the half. Then the half of the half. And so on. Of course in continuing to repeat this operation, the quatity tends to $\:0\:$. But a small and more and more smaller quantity always remains to be again divided in two. It's not exactly zero. It is an infinitesimal on the common sens.
More expanation in the above link and in : https://en.wikipedia.org/wiki/Infinitesimal
Comment :
In fact, "infinitesimal" is an abstract concept. Think also to another abstract concept : "Infinity" is an unbounded quantity that is greater than every real number. Both abstract concepts cannot be represented in real world on a concrete manner. Nevertheless, they can be intuitively understood.
