in·​fin·​i·​tes·​i·​mal | \ (ˌ)in-ˌfi-nə-ˈte-sə-məl How to pronounce infinitesimal (audio) , -zə-məl\

Definition of infinitesimal

 (Entry 1 of 2)

1 : immeasurably or incalculably small an infinitesimal difference
2 : taking on values arbitrarily close to but greater than zero



Definition of infinitesimal (Entry 2 of 2)

: an infinitesimal quantity or variable

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Other Words from infinitesimal


infinitesimally \ (ˌ)in-​ˌfi-​nə-​ˈte-​sə-​mə-​lē How to pronounce infinitesimally (audio) , -​zə-​mə-​ \ adverb

What is the origin of infinitesimal?


Infinite, as you probably know, means "endless" or "extending indefinitely." It is ultimately from Latin infinitus, the opposite of finitus, meaning "finite." The notion of smallness in infinitesimal derives from the mathematical concept that a quantity can be divided endlessly; no matter how small, it can be subdivided into yet smaller fractions, or "infinitesimals." The concept was still in its infancy in 1710 when Irish philosopher George Berkeley observed that some people "assert there are infinitesimals of infinitesimals of infinitesimals, etc., without ever coming to an end." He used the adjective in a mathematical sense, too, referring to "infinitesimal parts of finite lines." Less than a quarter century later, the adjective had acquired a general sense applicable to anything too small to be measured.

Examples of infinitesimal in a Sentence


an infinitesimal moment in time a soft drink with only an infinitesimal amount of caffeine

Recent Examples on the Web: Adjective

There has been some debate in the comments section regarding an answer given by Michael, who treated the multidimensional figure purely mathematically and came up with an answer of less than 50 percent for a small, but not infinitesimal, change. Quanta Magazine, "Solution: ‘Which Forecasts Are True?’," 26 Oct. 2016 Instead, there were centuries of infinitesimal changes. The Economist, "Latin is dead—yet it also lives on," 8 June 2019 Meanwhile, paid family leave for many American workers is infinitesimal or nonexistent, meaning that for those who do need to take care of a family member, there’s often no choice but to quit work. Anna North, Vox, "You’ve heard that women make 80 cents to men’s dollar. It’s much worse than that.," 2 Apr. 2019 The odds of otherwise healthy people facing hospitalization is even lower than this infinitesimal amount. Jim Prevor, WSJ, "Lettuce Try Not to Panic," 29 Nov. 2018 The good news, if there is any, is that Windows Mobile market share was always tiny to begin with, and now is largely infinitesimal: 0.10 percent, according to NetMarketShare. Mark Hachman, PCWorld, "For some, the glory days of Microsoft are ending in about a year," 18 Jan. 2019 The reality, however, is that planning the coming summit meeting between President Trump and Kim Jong-un to discuss North Korea’s nuclear future will require deciding countless, infinitesimal details, often via tricky diplomatic negotiations. New York Times, "Planning Trump-Kim Meeting: Who Sits Where, What Will They Eat and Who Pays?," 3 June 2018 Still, by the five-year mark, the fish had almost died off in the lake — near-extinction of a species due to an infinitesimal amount of a hormone. Rachael Moeller Gorman, Good Housekeeping, "Is Your Tap Water Safe?," 15 Aug. 2012 And the marginal cost of overpaying is infinitesimal relative to that base. Peter Kafka, Recode, "Here’s what HBO’s new boss really said about the company’s plans under AT&T," 10 July 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'infinitesimal.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of infinitesimal


1710, in the meaning defined at sense 2


1706, in the meaning defined above

History and Etymology for infinitesimal


borrowed from New Latin infīnītēsimālis, from infīnītēsimus "infinite in rank" (from Latin infīnītus "having no limit, infinite entry 1" + -ēsimus, suffix of higher ordinal numbers) + Latin -ālis -al entry 1 — more at vigesimal


New Latin infīnītēsimus "infinite in rank" + -al entry 2 — more at infinitesimal entry 1

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Statistics for infinitesimal

Last Updated

30 Jun 2019

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Time Traveler for infinitesimal

The first known use of infinitesimal was in 1706

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More Definitions for infinitesimal



English Language Learners Definition of infinitesimal

: extremely small


in·​fin·​i·​tes·​i·​mal | \ in-ˌfi-nə-ˈte-sə-məl How to pronounce infinitesimal (audio) \

Kids Definition of infinitesimal

: extremely small The chance of winning is infinitesimal.

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