What does "infinitesimal" mean?

Infinitesimal: Infinitely or indefinitely small; less than any assignable quantity or value; very small. Infinitesimal calculus, the different and the integral calculus, when developed according to the method used by Leibnitz, who regarded the increments given to variables as infinitesimal.

Additional senses

  1. 2.An infinitely small quantity; that which is less than any assignable quantity.

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