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atom

 - 6 dictionary results

at⋅om

  [at-uhm]
Use atom in a Sentence
–noun
1. Physics.
a. the smallest component of an element having the chemical properties of the element, consisting of a nucleus containing combinations of neutrons and protons and one or more electrons bound to the nucleus by electrical attraction; the number of protons determines the identity of the element.
b. an atom with one of the electrons replaced by some other particle: muonic atom; kaonic atom.
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.
Origin:
1350–1400; ME attomos, athomus < L atomus < Gk átomos, n. use of átomos undivided, equiv. to a- a- 6 + tomós divided, verbid of témnein to cut

Synonyms:
4. shred, speck, scintilla, iota, jot, whit.
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2009.
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at·om   (āt'əm)   


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n.  

    1. A part or particle considered to be an irreducible constituent of a specified system.

    2. The irreducible, indestructible material unit postulated by ancient atomism.

    3. 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.

    4. This unit regarded as a source of nuclear energy. See Table at subatomic particle.

  2. An extremely small part, quantity, or amount.

  3. Physics & Chemistry

    1. 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.

    2. This unit regarded as a source of nuclear energy. See Table at subatomic particle.


[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).]
The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Cultural Dictionary

atom

A unit of matter; the smallest unit of a chemical element. Each atom consists of a nucleus, which has a positive charge, and a set of electrons that move around the nucleus. (See Bohr atom.)

Note: Atoms link together to form molecules.
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
Cite This Source
Word Origin & History

atom 
1477, as a hypothetical body, the building block of the universe, from L. atomus (especially in Lucretius), from Gk. atomos "uncut," from a- "not" + tomos "a cutting," from temnein "to cut." An ancient term of philosophical speculation (in Leucippus, Democritus), revived 1805 by British chemist Dalton. Atomic is from 1678 as a philosophical term; scientific sense dates from 1811. Atomic energy first recorded 1906; atomic bomb first recorded 1914 in writings of H.G. Wells, who thought of it as a bomb "that would continue to explode indefinitely." Atom bomb is from 1945; Atomic Age is from 1945.
"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.
Online Etymology Dictionary, © 2001 Douglas Harper
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Medical Dictionary

Main Entry: at·om
Pronunciation: 'at-&m
Function: noun
: the smallest particle of an element that can exist either alone or in combination —atom·ic /&-'täm-ik/ adjective —atom·i·cal·ly /-i-k(&-)lE/ adverb
Merriam-Webster's Medical Dictionary, © 2002 Merriam-Webster, Inc.
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Medical Dictionary

atom at·om (āt'əm)
n.

  1. 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.

  2. This unit regarded as a source of nuclear energy.

  3. A part or particle considered to be an irreducible constituent of a specified system.

  4. The irreducible, indestructible material unit postulated by ancient atomism.

  5. An extremely small part, quantity, or amount.

a·tom'ic (ə-tŏm'ĭk) adj.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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