Infinitesimal

In`fin*i*tes"i*mal (?), a. [Cf. F. infinitésimal, fr. infinitésime infinitely small, fr. L. infinitus. See Infinite, a.] 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.

In`fin*i*tes"i*mal, n. (Math.) An infinitely small quantity; that which is less than any assignable quantity.