Atom

Pronunciation

UK IPA: /ËˆatÉ™m/
US IPA: /ËˆÃ¦É¾É™m/

Alternative forms

atomus obsolete

Origin

From Middle French atome, from Latin atomus ("smallest particle"), from Ancient Greek á¼„Ï„Î¿Î¼Î¿Ï‚ (atomos, "indivisible"), from á¼€- (a-, "not") + Ï„ÎÎ¼Î½Ï‰ (temnÅ, "I cut").

Full definition of atom

Noun

atom

(plural atoms)

(now historical) The smallest medieval unit of time, equal to fifteen ninety-fourths of a second. from 10th c.
(history of science) A hypothetical particle posited by Greek philosophers as an ultimate and indivisible component of matter. from 15th c.
(physics, chemistry) 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. from 16th c.
A molecule is a close combination of atoms.

2013, Katie L. Burke, In the News, Oxygen levels on Earth skyrocketed 2.4 billion years ago, when cyanobacteria evolved photosynthesis:.... 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.

A mote of dust in a sunbeam. from 16th c.
The smallest, indivisible constituent part or unit of something. (Now generally interpreted as a figurative use of the physics sense, above.) from 17th c.

1835, Sir John Ross, Sir James Clark Ross, Narrative of a Second Voyage in Search of a North-west Passage …, Volume 1'', pp.284-5Towards the following morning, the thermometer fell to 5°; and at daylight, there was not an atom of water to be seen in any direction.

A very small amount (of something immaterial); a whit. from 17th c.

1873, Isabella Macdonald Alden (as "Pansy"), Three People, Western Tract and Book Society (1873), page 325:"I have hardly the faintest atom of hope," answered this honest, earnest man.
Orwell Animal Farm|1... those of us who are capable of it are forced to work to the last atom of our strength

(mathematics) A non-zero member of a Boolean algebra that is not a union of any other elements. from 20th c.
(computing, programming, Lisp) An individual number or symbol, as opposed to a list. A scalar value.

Synonyms

(small amount) see also .