infinitesimal
Americanadjective
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exceedingly small; minute.
Capillaries, the infinitesimal vessels in our circulatory system, are small enough that red blood cells must flow through them single-file.
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Mathematics.
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immeasurably small; less than an assignable quantity.
An infinitesimal number is never zero, but it comes pretty close.
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of, relating to, or involving variables having zero as a limit.
infinitesimal calculus.
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noun
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an infinitesimal quantity.
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Mathematics. a variable having zero as a limit.
adjective
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infinitely or immeasurably small
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maths of, relating to, or involving a small change in the value of a variable that approaches zero as a limit
noun
Other Word Forms
- infinitesimality noun
- infinitesimally adverb
- infinitesimalness noun
Etymology
Origin of infinitesimal
First recorded in 1645–55; from New Latin infīnītēsim(us), equivalent to Latin infīnīt(us) infinite + -ēsimus suffix of ordinal numerals + -al 1
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Suddenly, the infinitesimal chances of the U.S.—down to 0.1% at one point during the day, according to Data Golf—began to creep upward with wins from its first two players.
From The Wall Street Journal • Sep. 28, 2025
Art often is just a business, but a dangerous one: Changing people by an infinitesimal degree, Castleberry knows, has a way of thoroughly warping and wrecking human lives.
From Los Angeles Times • Mar. 6, 2025
But you should not worry unduly, the effect will be infinitesimal.
From BBC • Oct. 21, 2023
El universo tal como lo conocemos ahora tiene 14 mil millones de años, lo que parece mucho tiempo, pero es solo una porción infinitesimal de los billones y trillones de años de oscuridad por venir.
From New York Times • May 6, 2023
His shoulders are hunched up around his ears so his strawberry hair disappears into his collar, and the infinitesimal tilt of his head tells me he’s been listening to everything we’ve said.
From "Girl in the Blue Coat" by Monica Hesse
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
