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

Keep scrolling for more

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

Adjective an infinitesimal moment in time a soft drink with only an infinitesimal amount of caffeine
Recent Examples on the Web: Adjective There are still people whose traces on Google are infinitesimal or nonexistent, and a good many things remain insufficiently archived. Maël Renouard, Harper's Magazine, "To Infinity and Beyond," 27 Apr. 2020 Its allure lies in its recognition that the most infinitesimal changes at the outset can lead almost identical systems into drastically differing directions over time. Martin Weil,, "Mitchell Feigenbaum, an architect of chaos theory, dies at 74," 14 July 2019 Its allure lies in its recognition that the most infinitesimal changes at the outset can lead almost identical systems into drastically differing directions over time. Martin Weil, Washington Post, "Mitchell Feigenbaum, an architect of chaos theory, dies at 74," 12 July 2019 The cost of storage is infinitesimal compared to the costs of not having these supplies on hand, and a well-functioning government would have recognized this and planned accordingly. Joseph E. Stiglitz, Time, "Why Our Affluent Society is Facing Shortages in the Face of the Coronavirus Pandemic?," 27 Mar. 2020 Since such craft have no more than an infinitesimal chance of being found, radio broadcasts from Earth, travelling at the speed of light, are more likely to make contact. The Economist, "How to talk to aliens," 28 Nov. 2019 The board will handle an infinitesimal slice of those, maybe 25 or 30 in its first year—and Facebook is obliged to respect its decisions only in those individual cases. Steven Levy, Wired, "Why Mark Zuckerberg’s Oversight Board May Kill His Political Ad Policy," 28 Jan. 2020 Think of the World Wide Web, the power grid and the universe, of which the Milky Way is an infinitesimal node in a seemingly boundless network of galaxies. Max Bertolero, Scientific American, "How the Mind Emerges from the Brain's Complex Networks," 11 July 2019 The margin separating one winner from the next is often infinitesimal. Cnt Editors, Condé Nast Traveler, "How Do the Readers' Choice Awards Work?," 7 Oct. 2019 Recent Examples on the Web: Noun 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, "Is Infinity Real?," 16 June 2016

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.

See More

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

Keep scrolling for more

Learn More about infinitesimal

Time Traveler for infinitesimal

Time Traveler

The first known use of infinitesimal was in 1706

See more words from the same year

Listen to Our Podcast about infinitesimal

Statistics for infinitesimal

Last Updated

4 May 2020

Cite this Entry

“Infinitesimal.” Dictionary, Merriam-Webster, Accessed 26 May. 2020.

Keep scrolling for more

More Definitions for infinitesimal


How to pronounce infinitesimal (audio)

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.

Keep scrolling for more

Comments on infinitesimal

What made you want to look up infinitesimal? Please tell us where you read or heard it (including the quote, if possible).


See Definitions and Examples »

Get Word of the Day daily email!

Test Your Vocabulary

Obscure Shapes

  • a pile of three dimensional shapes in green
  • Something that is ooid is shaped like:
Spell It

Can you spell these 10 commonly misspelled words?

Dictionary Devil

Test Your Knowledge - and learn some interesting things along the way.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!