[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 infinitesimal

Contemporary Examples of infinitesimal

Historical Examples of infinitesimal

  • To be sure, the wage was infinitesimal, while the toil was body-breaking soul-breaking.

    Within the Law

    Marvin Dana

  • Here we find no infinitesimal subdivision and no multiplicity of crops.

    In the Heart of Vosges

    Matilda Betham-Edwards

  • Every beginning is infinitesimal, and wrapt in the mystery of creation.

    Salted With Fire

    George MacDonald

  • It is not the infinitesimal of time, but the negative of time.

  • Yet surely (replied Socrates) that is only an infinitesimal part of generalship.

British Dictionary definitions for infinitesimal



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 infinitesimal

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

infinitesimal in Science




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.