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

Other Words from infinitesimal


infinitesimally \ (ˌ)in-​ˌfi-​nə-​ˈte-​sə-​mə-​lē How to pronounce infinitesimal (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 infīnītus, the opposite of fīnītus, 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 the early 1700s 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 word in a mathematical sense, too, referring to "infinitesimal parts of finite lines." Later, the adjectival form acquired a general sense applicable to anything too small to be measured.

Examples of infinitesimal in a Sentence

Adjective an infinitesimal moment in time a soft drink with only an infinitesimal amount of caffeine
Recent Examples on the Web: Adjective Then in the nineteenth century, the cell was discovered, and the single machine in its turn was found to be the product of millions of infinitesimal machines—the cells. Loren C. Eiseley, Harper’s Magazine , 27 Apr. 2022 In the original Big Bang, there’s a core, an infinitesimal singularity that brought the whole universe bursting into creation. Los Angeles Times, 5 Apr. 2022 But Apple has frequently targeted entities that have nothing to do with tech or that are infinitesimal in size. New York Times, 11 Mar. 2022 An attorney for the airmen argued during a 2019 hearing that the odds of transmitting HIV in combat are infinitesimal and should not limit their deployment or lead to their discharge. Fox News, 10 Apr. 2022 To record the insects’ infinitesimal flight patterns, experimenters placed the creatures in a transparent chamber and filmed them with two high-speed cameras at nearly 4,000 frames per second during a battery of tests. Jack Tamisiea, Scientific American, 21 Mar. 2022 The movie’s design also offers a handful of piquant touches, from the infinitesimal points of Catwoman’s mask-ears to the cable zip line that the Batman discharges for rapid rescues and escapes. Richard Brody, The New Yorker, 9 Mar. 2022 Moreover, the drug supply has become exponentially more dangerous since then, Rivera said, as heroin is now cut with fentanyl, which can prove fatal even in infinitesimal doses. Los Angeles Times, 23 Feb. 2022 From here, the theme shifts to air pollution, which endangers spiders and humans alike, especially the infinitesimal, breathable grains of carbon called particulate matter. New York Times, 20 Feb. 2022 Recent Examples on the Web: Noun Since then, Parker has persistently sought meaning in the infinitesimal and evanescent. Jonathon Keats, Forbes, 20 May 2022 This led to his theory of surreal numbers — a huge new number system containing not only all the real numbers, but also a boggling collection of infinites and infinitesimals, like π minus 1 divided by the cube root of infinity. New York Times, 16 May 2020 Infinities implicitly pervade many familiar mathematical concepts, such as the idea of points as mentioned above, the idea of the continuum, and the concept of infinitesimals in calculus. Quanta Magazine, 16 June 2016 See More

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.

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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The first known use of infinitesimal was in 1706

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Dictionary Entries Near infinitesimal

infinite series


infinitesimal calculus

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Last Updated

11 May 2022

Cite this Entry

“Infinitesimal.” Dictionary, Merriam-Webster, Accessed 22 May. 2022.

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More Definitions for infinitesimal


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.

More from Merriam-Webster on infinitesimal

Nglish: Translation of infinitesimal for Spanish Speakers Encyclopedia article about infinitesimal


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