atom

noun

at·​om ˈa-təm 

1

a

: the smallest particle of an element that can exist either alone or in combination

an atom of hydrogen

b

: the atom considered as a source of vast potential constructive or destructive energy

… a largely forgotten legacy of this country's conquest of the atom.

—William J. Broad

… when Congress passed the Atomic Energy Act in 1954 and allowed private utilities to "harness the atom."

—Barry Werth

2

: a tiny particle : bit

There's not an atom of truth in what he said.

3

: one of the minute indivisible particles of which according to ancient materialism (see materialism sense 1a) the universe is composed

Did you know?

Some ancient philosophers believed that matter is infinitely divisible, that any particle, no matter how small, can always be divided into smaller particles. Others believed that there must be a limit and that everything in the universe must be made up of tiny indivisible particles. Such a hypothetical particle was called atomos in Greek, which means “indivisible.” According to modern atomic theory, all matter is made up of tiny particles named atoms from the ancient Greek atomos. However, it has turned out that atoms are not indivisible after all. Indeed, the splitting of atoms can be used to produce vast amounts of energy, as in atom bombs.

Synonyms

• bit
• crumb
• dribble
• fleck
• flyspeck
• grain
• granule
• molecule
• morsel
• mote
• nubbin
• nugget
• particle
• patch
• scrap
• scruple
• snip
• snippet
• speck
• tittle

Examples of atom in a Sentence

There is not an atom of truth to what he said.

give me just one atom of information about the novel's surprise ending

Recent Examples on the Web

Like, is anyone talking about the inventor of the atom bomb in their lives? —Zack Sharf, Variety, 25 Mar. 2024

The experimental investigations mark the next stage in the quest to understand the particle that anchors every atom and makes up the bulk of our world. —Quanta Magazine, 14 Mar. 2024

The historical drama, based on the life of physicist J. Robert Oppenheimer and his creation of the atom bomb, became the highest-grossing biopic of all-time in 2023. —Brendan Le, Peoplemag, 10 Mar. 2024

Oklo, which Altman also chairs, is focused on the opposite reaction, fission, which generates energy by splitting an atom; fusion does so by merging atomic nuclei. Representatives for Altman, through his special acquisition company AltC, didn’t respond to a request for comment. —Emily Pandise, NBC News, 7 Mar. 2024

For example, a scientist working for British intelligence was able to discern, just by reading the physics journal Physikalische Zeitschrift, that, as of 1941, the Nazis had not committed the resources needed to make an atom bomb. —Claudia Roth Pierpont, The New Yorker, 19 Feb. 2024

The atom bomb could fall, or Martians could arrive, all that sort of thing. —Angela Watercutter, WIRED, 10 Feb. 2024

James Hansen, former director of NASA's Goddard Institute for Space Studies, has estimated that the energy building up in the atmosphere from our greenhouse gas emissions is equivalent to that from 800,000 Hiroshima atom bombs exploding each and every day. —Tom Yulsman, Discover Magazine, 29 Jan. 2024

A lot of that was necessary in Oppenheimer, Nolan’s biopic of the life of J. Robert Oppenheimer, the man who led the Manhattan Project—the government program that developed the atom bombs that were dropped on Hiroshima and Nagasaki at the end of World War II. —Jeffrey Kluger, TIME, 29 Jan. 2024

Word History

Etymology

Middle English, from Latin atomus, from Greek atomos, from atomos indivisible, from a- + temnein to cut

First Known Use

15th century, in the meaning defined at sense 3

Phrases Containing atom

• atom smasher

Kids Definition

atom

noun

at·​om ˈat-əm 

1

: a tiny particle : bit

2

: the smallest particle of an element that has the properties of the element and can exist either alone or in combination

3

: the atom considered as a source of vast potential energy

Etymology

Middle English atom "particle," from Latin atomus (same meaning), derived from Greek atomos "unable to be divided," from a- "not" and temnein "to cut"

Medical Definition

atom

noun

at·​om ˈat-əm 

: the smallest particle of an element that can exist either alone or in combination

atomic

ə-ˈtäm-ik 

adjective

atomically

-i-k(ə-)lē 

adverb