Definition of atom
1a : 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 1a) the universe is composed
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>
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.
Origin and Etymology of atom
Middle English, from Latin atomus, from Greek atomos, from atomos indivisible, from a- + temnein to cut
First Known Use: 15th century
ATOM Defined for English Language Learners
Definition of atom for English Language Learners
: the smallest particle of a substance that can exist by itself or be combined with other atoms to form a molecule
: a very small amount of something
ATOM Defined for Kids
History for atom
The English word atom came from a Greek word atomos, meaning “not able to be divided.” Ancient Greek philosophers believed that matter could only be divided to the very smallest particles, atoms, which could not be further divided. Modern science revived the atom idea, but it was discovered that even atoms could be split, and that doing so produced great amounts of energy.
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