attom

Noun

atom (plural atoms)

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...2013 September–October, Katie L. Burke, “In the news: Photosynthesis precursor”, in American Scientist, archived from the original on 13 Apr 2016
2. A hypothetical particle posited by Greek philosophers as an ultimate and indivisible component of matter.
3. (now generally regarded figuratively) 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 Ice—Become Fixed for the Winter—Summary of the Month.”, in Narrative of a Second Voyage in Search of a North-west...
4. In logical atomism, a fundamental fact that cannot be further broken down.
5. (historical) The smallest medieval unit of time, equal to fifteen ninety-fourths of a second.
6. A mote of dust in a sunbeam.

See all 13 meanings of atom