[in-fin-i-tes-uh-muh l]


indefinitely or exceedingly small; minute: infinitesimal vessels in the circulatory system.
immeasurably small; less than an assignable quantity: to an infinitesimal degree.
of, relating to, or involving infinitesimals.


an infinitesimal quantity.
Mathematics. a variable having zero as a limit.

Origin of infinitesimal

1645–55; < New Latin infīnītēsim(us), equivalent to Latin infīnīt(us) infinite + -ēsimus suffix of ordinal numerals + -al1
Related formsin·fin·i·tes·i·mal·i·ty, in·fin·i·tes·i·mal·ness, nounin·fin·i·tes·i·mal·ly, adverb Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for infinitesimally

Contemporary Examples of infinitesimally

Historical Examples of infinitesimally

  • Just think—that sparrow when we last saw it was infinitesimally small.

    The Girl in the Golden Atom

    Raymond King Cummings

  • He must have been infinitesimally small; but that did not matter.

    Mystic London:

    Charles Maurice Davies

  • Their success, of which so much is said in England and America, is "infinitesimally small."

    From Egypt to Japan

    Henry M. Field

  • Then carefully, ever so infinitesimally, he adjusted a knob on the device.

  • The trouble is that they are so small, so infinitesimally small, almost.

British Dictionary definitions for infinitesimally



infinitely or immeasurably small
maths of, relating to, or involving a small change in the value of a variable that approaches zero as a limit


maths an infinitesimal quantity
Derived Formsinfinitesimally, adverb
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for infinitesimally



1710 (1650s as a noun), "infinitely small," from Modern Latin infinitesimus, from Latin infinitus "infinite" (see infinite) + -esimus, as in centesimus "hundredth." Related: Infinitesimally.

Online Etymology Dictionary, © 2010 Douglas Harper

Science definitions for infinitesimally




Capable of having values approaching zero as a limit.


A function or variable continuously approaching zero as a limit.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.