Infinitesimal /infinəˈtes(ə)m(ə)l / noun, adj.

Definition:  Infinitesimal means extremely small. The word is primarily used as an adjective; however, in mathematics, it is utilized as a noun meaning indefinitely, or infinitely, small.

Etymology: The word can be traced back to the middle of the seventeenth century, where it developed through the merging of the English word infinite and the modern Latin word infinitesimus, the word infinitesimus itself having derived from Old Latin’s infinitus.

In a Sentence

The amount of radioactivity present in the provided samples was infinitesimal.

Even an infinitesimal change in average global temperature can lead to devastating environmental repercussions.

While only an infinitesimal amount of purchases were once made using cryptocurrency, as the form of currency has gained popularity and market momentum, more and more businesses are accepting it as a valid form of payment.

One of the most valuable skills an investigator can demonstrate out in the field is the ability to notice even the most infinitesimal bits of evidence.

Synonyms

Minuscule, Tiny, Minute, Microscopic, Imperceptible, Indiscernible

Antonyms 

Huge, Enormous, Immense, Gigantic, Massive, Colossal