[ in-fin-i-tes-uh-muhl ]
See synonyms for: infinitesimalinfinitesimalsinfinitesimalness on

  1. exceedingly small; minute: Capillaries, the infinitesimal vessels in our circulatory system, are small enough that red blood cells must flow through them single-file.

  2. Mathematics.

    • immeasurably small; less than an assignable quantity:An infinitesimal number is never zero, but it comes pretty close.

    • of, relating to, or involving variables having zero as a limit:infinitesimal calculus.

  1. an infinitesimal quantity.

  2. Mathematics. a variable having zero as a limit.

Origin of infinitesimal

First recorded in 1645–55; from New Latin infīnītēsim(us), equivalent to Latin infīnīt(us) infinite + -ēsimus suffix of ordinal numerals + -al1

Other words from infinitesimal

  • in·fin·i·tes·i·mal·i·ty [in-fin-i-tes-uh-mal-i-tee], /ˌɪn fɪn ɪˌtɛs əˈmæl ɪ ti/, in·fin·i·tes·i·mal·ness, noun
  • in·fin·i·tes·i·mal·ly, adverb Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use infinitesimal in a sentence

British Dictionary definitions for infinitesimal


/ (ˌɪnfɪnɪˈtɛsɪməl) /

  1. infinitely or immeasurably small

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

  1. maths an infinitesimal quantity

Derived forms of infinitesimal

  • infinitesimally, 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

Scientific definitions for infinitesimal


[ ĭn′fĭn-ĭ-tĕsə-məl ]

  1. Capable of having values approaching zero as a limit.

  1. 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.