atom

Meanings

1. 1
   noun

   The smallest part of a chemical element that can exist.

   Three oxygen atoms join together to form the molecule ozone.

2. 2
   noun

   A very small amount of something.

   There wasn't an atom of truth in what he said.

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Simplified etymology

Atom comes through Latin atomus from Greek atomos, meaning “indivisible” or “unable to be cut.” English first used it for an indivisible entity or the smallest unit of time, and from the mid-16th century it was applied in the ancient Greek sense to a supposed ultimate particle of matter. In the early 19th century John Dalton gave the term its modern scientific role, though later discoveries showed that atoms themselves can be divided.

From Middle English attome, from Middle French athome, from Latin atomus (“smallest particle”), from Ancient Greek ἄτομος (átomos, “indivisible”), from ἀ- (a-, “not”) + τέμνω (témnō, “to cut”, o-grade in τομ-) + -ος (-os). Atoms are so named because they were historically thought up as to be the smallest unit of matter, and thus indivisible. Doublet of atomus.

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