m]
| 1. | Physics.
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| 2. | Energy. this component as the source of nuclear energy. |
| 3. | a hypothetical particle of matter so minute as to admit of no division. |
| 4. | anything extremely small; a minute quantity. |

at·om (āt'əm) ![]() (click for larger image in new window) n.
[Middle English attome, from Latin atomus, from Greek atomos, indivisible, atom : a-, not; see a-1 + tomos, cutting (from temnein, to cut; see tem- in Indo-European roots).] |
"When you can drop just one atomic bomb and wipe out Paris or Berlin, war will have become monstrous and impossible." [S. Strunsky, "Yale Review," January 1917]Atomize "reduce a liquid to a fine mist" is from 1865; sense of "to destroy with atomic weapons" is from 1945.
atom at·om (āt'əm)
n.
A unit of matter, the smallest unit of an element, having all the characteristics of that element and consisting of a dense, central, positively charged nucleus surrounded by a system of electrons. The entire structure has an approximate diameter of 10-8 centimeter and characteristically remains undivided in chemical reactions except for limited removal, transfer, or exchange of certain electrons.
This unit regarded as a source of nuclear energy.
A part or particle considered to be an irreducible constituent of a specified system.
The irreducible, indestructible material unit postulated by ancient atomism.
An extremely small part, quantity, or amount.
| atom (āt'əm) Pronunciation Key
The smallest unit of an element, consisting of at least one proton and (for all elements except hydrogen) one or more neutrons in a dense central nucleus, surrounded by one or more shells of electrons. In electrically neutral atoms, the number of protons equals the number of electrons. Atoms remain intact in chemical reactions except for the removal, transfer, or exchange of certain electrons. Compare compound. See also ion, isotope, orbital. |