noun in·fin·i·tes·i·mal \ (ˌ)in-ˌfi-nə-ˈte-sə-məl , -zə-məl \
Updated on: 19 May 2018

Definition of infinitesimal

: an infinitesimal quantity or variable

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Origin and Etymology of infinitesimal

New Latin infinitesimus infinite in rank, from Latin infinitus

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Definition of infinitesimal

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


play \(ˌ)in-ˌfi-nə-ˈte-sə-mə-lē, -zə-mə-\ adverb

Examples of infinitesimal in a Sentence

  1. an infinitesimal moment in time

  2. a soft drink with only an infinitesimal amount of caffeine

Recent Examples of infinitesimal from the Web

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.

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.

First Known Use of infinitesimal


in the meaning defined at sense 1

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INFINITESIMAL Defined for English Language Learners


Definition of infinitesimal for English Language Learners

  • : extremely small

INFINITESIMAL Defined for Kids


adjective in·fin·i·tes·i·mal \ in-ˌfi-nə-ˈte-sə-məl \

Definition of infinitesimal for Students

: extremely small
  • The chance of winning is infinitesimal.

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to fill with foolish love or admiration

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