Atom
name, noun ·Very common ·Middle school level
Definitions
- 1 The smallest possible amount of matter which still retains its identity as a chemical element, now known to consist of a nucleus surrounded by electrons.
"Oxygen levels on Earth skyrocketed 2.4 billion years ago, when cyanobacteria evolved photosynthesis: the ability to convert water and carbon dioxide into carbohydrates and waste oxygen using solar energy. The evolutionary precursor of photosynthesis is still under debate, and a new study sheds light. The critical component of the photosynthetic system is the water-oxidizing complex, made up of manganese atoms and a calcium atom."
- 2 (nontechnical usage) a tiny piece of anything wordnet
- 3 A hypothetical particle posited by Greek philosophers as an ultimate and indivisible component of matter.
- 4 (physics and chemistry) the smallest component of an element having the chemical properties of the element wordnet
- 5 The smallest, indivisible constituent part or unit of something.
"Towards the following morning, the thermometer fell to 5°; and at daylight, there was not an atom of water to be seen in any direction."
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- 6 In logical atomism, a fundamental fact that cannot be further broken down.
- 7 The smallest medieval unit of time, equal to fifteen ninety-fourths of a second. historical
- 8 A mote of dust in a sunbeam.
- 9 A very small amount; a whit.
""Doctor, tell me one word more," said Theodore, quivering with suppressed emotion. "How do you think it will end?" / "I have hardly the faintest atom of hope," answered this honest, earnest man."
- 10 An individual number or symbol, as opposed to a list; a scalar value.
- 11 An integer representing a particular string.
- 12 A non-zero member of a partially ordered set that has only zero below it (assuming that the poset has a least element, its "zero").
"In a Venn diagram, an atom is depicted as an area circumscribed by lines but not cut by any line."
- 13 An element of a set that is not itself a set; an urelement.
- 14 An age group division in hockey for nine- to eleven-year-olds. Canada, attributive, usually
- 1 A Meitei surname from Manipuri
Antonyms
All antonymsExample
More examples"A water molecule has two hydrogen atoms and one oxygen atom."
Etymology
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.
From Manipuri ꯑꯇꯣꯝ (ʼatom).
Related phrases
More for "atom"
Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.