atom

Noun

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...

   Meronyms: proton neutron electron

2. A hypothetical particle posited by Greek philosophers as an ultimate and indivisible component of matter.
3. 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. - 1835, John Ross, James Clark Ross, “Chapter XXXIV. Labour in Cutting through the...
   • But at this critical moment the pirate astern sent a mischievous shot and knocked one of the men to atoms at the helm. - 1863, Charles Reade, Hard Cash:
4. In logical atomism, a fundamental fact that cannot be further broken down.
5. The smallest medieval unit of time, equal to fifteen ninety-fourths of a second.
6. A mote of dust in a sunbeam.
7. 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. - 1873, “Pansy”...
   • We are born, we are given just so much food as will keep the breath in our bodies, and those of us who are capable of it are forced to work to the last atom of our strength; and the very instant that our usefulness has...

   Synonyms: particle speck ace atom atomy aught bissel bit crumb glimpse dab damn dash diddly glint dot spatter drop dusting fleck glimmer hint flip flyspeck

8. An individual number or symbol, as opposed to a list; a scalar value.
9. An integer representing a particular string.

   Coordinate Terms: quark

10. 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.

    Antonyms: coatom

11. An element of a set that is not itself a set; an urelement.
12. An age group division in hockey for nine- to eleven-year-olds.