1
Nearly immeasurable quantity
An amount too small to matter at an ordinary scale.
Example
The treatment produced only an infinitesimal change in average temperature.
infinitesimal
/ˌɪnfɪnɪˈtesɪməl/ · in-fin-ih-TES-ih-muhladjective
Extremely small; approaching zero in size or amount.
Use infinitesimal for a quantity or difference so tiny that it is almost negligible, especially in scientific or mathematical contexts.
What infinitesimal Really Means
The word becomes easier to use when its closely related senses are separated and compared.
2
Mathematical increment
A value considered arbitrarily close to zero.
Example
The proof examines an infinitesimal change in the curve's position.
3
Tiny practical effect
A difference whose real-world impact is negligible.
Example
For most users, the two designs differ by an infinitesimal amount.
Use infinitesimal Naturally
Notice how the surrounding noun or clause reveals the exact shade of meaning.
The treatment produced only an infinitesimal change in average temperature.
An infinitesimal crack can expand under repeated pressure.
The probability of that exact sequence is infinitesimal.
Precision Matters
Infinitesimal overlaps with several common words, but each carries a different emphasis.
infinitesimal
vs.Often suggests a quantity approaching zero.
minute
Means extremely small but not necessarily negligible.
infinitesimal
vs.Describes actual size or amount.
imperceptible
Describes inability to be perceived.
infinitesimal
vs.Concerns magnitude.
trivial
Concerns importance or consequence.
infinitesimal
vs.Is vanishingly small.
substantial
Is considerable in size or importance—the contrast.
Test infinitesimal in Context
The difference is extremely small and effectively negligible.
1
Although the instrument detected a difference between the samples, the change was so ___ that it could not affect the study's practical conclusion.