from The American Heritage® Dictionary of the English Language, 5th Edition.

  • adjective Immeasurably or incalculably minute.
  • adjective Mathematics Capable of having values approaching zero as a limit.
  • noun An immeasurably or incalculably minute amount or quantity.
  • noun Mathematics A function or variable continuously approaching zero as a limit.

from The Century Dictionary.

  • Infinitely or indefinitely small; less than any assignable quantity.
  • noun In mathematics, a fictitious quantity so small that by successive additions to itself no sensible quantity, such as the unit of quantity, could ever be generated.

from the GNU version of the Collaborative International Dictionary of English.

  • adjective Infinitely or indefinitely small; less than any assignable quantity or value; very small.
  • adjective the different and the integral calculus, when developed according to the method used by Leibnitz, who regarded the increments given to variables as infinitesimal.
  • noun (Math.) An infinitely small quantity; that which is less than any assignable quantity.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • adjective Incalculably, exceedingly, or immeasurably minute; vanishingly small.
  • adjective mathematics Of or pertaining to values that approach zero as a limit.
  • adjective informal Very small.
  • noun mathematics A non-zero quantity whose magnitude is smaller than any positive number (by definition it is not a real number).

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun (mathematics) a variable that has zero as its limit
  • adjective infinitely or immeasurably small


from The American Heritage® Dictionary of the English Language, 4th Edition

[From New Latin īnfīnītēsimus, infinite in rank, from Latin īnfīnītus, infinite; see infinite.]


  • That is the one and only actual meaning of the use of the term infinitesimal by Leibniz.

    LaRouche's Latest

  • BTW, "infinitesimal" is an actual word and not made up by Obama.

    Obama says differences with Clinton 'infinitesimal'

  • Twice an infinitesimal is an infinitesimal that is twice as big.

    The Volokh Conspiracy » “Year of Our Lord”

  • To Jack from Texas, I know the Texas education system must be in terrible shape with Republicans running that state for so long, but infinitesimal is not a made up word, just do a search, here is the definition:

    Obama says differences with Clinton 'infinitesimal'

  • Say, rather, "infinitesimal" - much like the snowflake that starts an avalanche.

    Do bloggers create the buzz?

  • This has been achieved in two essentially different ways, the one providing a rigorous formulation of the idea of infinitesimal number, the other of infinitesimal magnitude.

    Continuity and Infinitesimals

  • Bolzano also formulated a definition of the derivative of a function free of the notion of infinitesimal (see Bolzano [1950]).

    Continuity and Infinitesimals

  • Only by reducing this element of free will to the infinitesimal, that is, by regarding it as an infinitely small quantity, can we convince ourselves of the absolute inaccessibility of the causes, and then instead of seeking causes, history will take the discovery of laws as its problem.

    War and Peace

  • In spite of the glowing reports issued annually from various foreign hospitals for natives, and the undeniable good, though desultory and practically infinitesimal, that is being worked by these institutions, we cannot blind ourselves to the fact that western medical science is not making more rapid strides than many other innovations in the great struggle against Chinese prejudice and distrust.

    Historic China, and other sketches

  • In particular, that potent instrument called the infinitesimal calculus, which Newton had invented for the investigation of nature, had become so far perfected that Laplace, when he attempted to unravel the movements of the heavenly bodies, found himself provided with a calculus far more efficient than that which had been available to Newton.

    Great Astronomers


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  • Also: Incredibly small; immeasurably or incalculably minute.

    December 31, 2007