atom

noun

at·om ˈa-təm

Synonyms of atom next

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

an atom of hydrogen

: 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

: a tiny particle : bit

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

: 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.

Example Sentences

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 The image represents the now-obsolete Bohr model of the atom, developed by 20th-century theoretical physicist Niels Bohr. —

Ariana Garcia, Chron, 12 May 2023 Differences in rainfall, latitude, temperature and soil conditions mean these atoms vary slightly across regions of the world, allowing researchers to map where the cotton in a pair of socks or bath towel has come from. —

Ana Swanson, New York Times, 7 Apr. 2023 In contrast, the intricate nanoscale architectures of structural color, some only a little larger than an individual atom, do not absorb light but reflect it into particular wavelengths. —

Tomas Weber, Smithsonian Magazine, 23 Dec. 2022 Scientists invented the Geiger counter while working on experiments to prove that the center of an atom has a high-density zone, called the nucleus. —

Kat Friedrich, Popular Mechanics, 12 Dec. 2022 That’s translated into more advanced, effective, and atrocious forms of violence, up to and including the atom bomb. —

Jon Blistein, Rolling Stone, 9 Sep. 2022 This beautiful duel set off numerous atom bombs of art: From Matisse alone, Portrait of Mlle Yvonne Landsberg, View of Notre-Dame, Bathers With a Turtle, Dance (I), not to mention the four huge, almost Mesopotamian bronze-back sculptures. —

Vulture, 3 May 2022 Viewers reported spectacular colors ranging from reds to greens and yellows—a variation caused by atoms of different elements reacting with the solar energy at different altitudes. —

Margaret Osborne, Smithsonian Magazine, 27 Apr. 2023 But here’s what was new: A team of scientists at the Chinese Academy of Sciences scanned 117 glass beads from Chang’e-5 and claimed most of them contained either water molecules or hydroxyls, molecules with an attached chemical group made of one hydrogen and one oxygen atom. —

Ned Potter, IEEE Spectrum, 12 Apr. 2023 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'atom.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

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

See more words from the same century

Cite this Entry

Style

“Atom.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/atom. Accessed 10 Jun. 2023.

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Kids Definition

atom

noun

at·om ˈat-əm

: a tiny particle : bit

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

: 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"