Source: The Collaborative International Dictionary of English v.0.48
Infinitesimal \In`fin*i*tes"i*mal\, a. [Cf. F. infinit['e]simal,
fr. infinit['e]sime infinitely small, fr. L. infinitus. See
Infinite, a.]
Infinitely or indefinitely small; less than any assignable
quantity or value; very small.
[1913 Webster]
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.
[1913 Webster]
Source: The Collaborative International Dictionary of English v.0.48
Infinitesimal \In`fin*i*tes"i*mal\, n. (Math.)
An infinitely small quantity; that which is less than any
assignable quantity.
[1913 Webster]