This section is from the Openstax University Physics: Volume 1 online textbook.

In physics, work is done on an object when energy is transferred to the object. In other words, work is done when a force acts on something that undergoes a displacement from one position to another. Forces can vary as a function of position, and displacements can be along various paths between two points. We first define the increment of work $\text dW$ done by a force $\mathbf F$ acting through an infinitesimal displacement $\text d\mathbf r$ as the dot product of these two vectors:

Is it simply just a very small displacement?


Yes, infinitesimal just means extremely close to zero.

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    $\begingroup$ Is $10^{-9}$ meters close enough to zero displacement to be an infinitesimal displacement? No. And neither is any other finite displacement. You are ignoring more than 300 years of calculus. $\endgroup$ – G. Smith Oct 20 '19 at 22:28
  • $\begingroup$ Hi G. I thought a layman's answer was needed. I picked the word extremely to suggest the limiting value of smallness. $\endgroup$ – Marco Ocram Oct 21 '19 at 6:31

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