Part of speech: adjective
Origin: Latin, mid-17th century
Examples of Infinitesimal in a sentence
"The weatherman said there's an infinitesimal chance it will rain today, but I'm still taking my jacket."
"Infinitesimal traces of chicken fell on the floor, but my dog immediately smelled them."
As an adjective, "infinitesimal" means "incredibly small" — or in a technical sense, too small to be measured by standard means. But it can also be used as a noun to describe an amount. In this sense it's mostly used by mathematicians for a number or quantity that can be divided endlessly into smaller fractions, or "infinitesimals."
Did you Know?
You might recognize the word "infinite" at the start of this long word, but it's not used to refer to endlessly long numbers. Instead, "infinitesimal" is a description of very small size. There may be an infinite number of fish in the ocean, but a single speck of plankton is infinitesimal.