atom

noun

at·​om ˈa-təm How to pronounce atom (audio)
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.

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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
The atoms in this liquid metallic hydrogen are squeezed so tightly that its electrons are free to roam. Benjamin Roulston, Discover Magazine, 7 Nov. 2024 The roughly 50,000 atoms in the gas lose any sense of identity, merging into a single state. Quanta Magazine, 6 Nov. 2024 Think about a nuclear fusion reaction in the core of a star, where two hydrogen atoms, each with a single proton, combine to become a helium atom, with two. Lane Sainty, The Arizona Republic, 3 Nov. 2024 Typically, the carbon atoms in these bonds, and the atoms attached to them, lie in the same geometric plane. Gordon G. Chang, Newsweek, 31 Oct. 2024 See all Example Sentences for atom 

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

Time Traveler
The first known use of atom was in the 15th century

Dictionary Entries Near atom

Cite this Entry

“Atom.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/atom. Accessed 22 Nov. 2024.

Kids Definition

atom

noun
at·​om ˈat-əm How to pronounce atom (audio)
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 How to pronounce atom (audio)
: the smallest particle of an element that can exist either alone or in combination
atomic adjective
atomically adverb

More from Merriam-Webster on atom

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