adjective / noun

infinitesimal

in-fin-ih-TES-ih-mul/ˌɪnfɪnɪˈtesɪml/

So small in magnitude as to approach zero.

The grain of sand looks infinitesimal on an adult's fingertip.

A tiny grain of sand on an adult fingertip, accompanied by a simple circular magnifying glass revealing the grain at larger scale.

Etymology

inLatinnot

+finitLatindefinite, limited

+esimalLatinordinal-forming ending

The “not limited” base combines with an ordinal ending like that in “hundredth.” The resulting word describes something infinitely small—less than any assignable quantity—and more generally something extremely tiny.

In context

Storytime Haven208:16

In just that infinitesimal space of time everything was changed. Old things passed away and all things became new.

📖 The Blue Castle by L. M. Montgomery | A Tale of Love & Freedom 💙✨

More examples

The fee represents an infinitesimal fraction of the total cost.
Even an infinitesimal change in temperature affects the measurement.
A positive infinitesimal is smaller than every positive real number.

Forms

infinitesimal · infinitesimals

infinitesimally adverb — To an extremely small degree.

Similar words

minuscule: Means extremely small without the mathematical suggestion of approaching zero.
tiny: Means very small, usually less emphatically than infinitesimal.
negligible: Emphasizes being too small to matter rather than size alone.