atom

[ at-uhm ]
/ ˈæt əm /
||

noun

Physics.
  1. 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.
  2. an atom with one of the electrons replaced by some other particle: muonic atom; kaonic atom.
Energy. this component as the source of nuclear energy.
a hypothetical particle of matter so minute as to admit of no division.
anything extremely small; a minute quantity.

Origin of atom

1350–1400; Middle English attomos, athomus < Latin atomus < Greek átomos, noun use of átomos undivided, equivalent to a- a-6 + tomós divided, verbid of témnein to cut
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for atom

British Dictionary definitions for atom

atom

/ (ˈætəm) /

noun

  1. the smallest quantity of an element that can take part in a chemical reaction
  2. this entity as a source of nuclear energythe power of the atom See also atomic structure
any entity regarded as the indivisible building block of a theory
the hypothetical indivisible particle of matter postulated by certain ancient philosophers as the fundamental constituent of matterSee also atomism
a very small amount or quantity; minute fragmentto smash something to atoms; there is not an atom of truth in his allegations

Word Origin for atom

C16: via Old French and Latin, from Greek atomos (n), from atomos (adj) that cannot be divided, from a- 1 + temnein to cut
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medicine definitions for atom

atom

[ ătəm ]

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.
Related formsa•tomic (ə-tŏmĭk) adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for atom

atom

[ ătəm ]

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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Culture definitions for atom

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 New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.