from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A part or particle considered to be an irreducible constituent of a specified system.
- n. The irreducible, indestructible material unit postulated by ancient atomism.
- n. An extremely small part, quantity, or amount.
- n. Physics & Chemistry 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.
- n. Physics & Chemistry This unit regarded as a source of nuclear energy. See Table at subatomic particle.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The smallest, indivisible constituent part or unit of something.
- n. 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.
- n. A non-zero member of a Boolean algebra that is not a union of any other elements.
- n. A theoretical particle of matter, imagined to be incapable of further division; the smallest possible unit of substance.
- n. The smallest medieval unit of time, equal to fifteen ninety-fourths of a second.
- n. An individual number or symbol, as opposed to a list. A scalar value.
- n. A very small amount.
from the GNU version of the Collaborative International Dictionary of English
- n. An ultimate indivisible particle of matter.
- n. An ultimate particle of matter not necessarily indivisible; a molecule.
- n. A constituent particle of matter, or a molecule supposed to be made up of subordinate particles.
- n. The smallest particle of matter that can enter into combination; one of the elementary constituents of a molecule.
- n. Anything extremely small; a particle; a whit.
- transitive v. To reduce to atoms.
from The Century Dictionary and Cyclopedia
- n. An extremely minute particle of matter: a term used generally with certain philosophic or scientific limitations.
- n. A particle of matter assumed not to be divided under the circumstances considered; a molecule.
- n. In chem. and physics, the unit of matter; the smallest mass of an element that exists in any molecule. The number of kinds of atoms is the same as the number of the elements. All atoms of the same element have the same constant weight. They are for the most part combined with other atoms, either of the same or of a different kind, forming molecules, and are indivisible by chemical force. The atom is sometimes called the chemical unit, in distinction from the molecule or physical unit, the latter being the smallest particle of any kind of matter which can exhibit all the properties of that matter; but atom is also sometimes used as synonymous with molecule in this sense.
- n. Hence Anything extremely small; a minute quantity: as, he has not an atom of sense.
- n. The smallest division of time, equal to about ⅙ of a second.
- n. Anything indivisible; an individual.
- To reduce to atoms; atomize.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. (physics and chemistry) the smallest component of an element having the chemical properties of the element
- n. (nontechnical usage) a tiny piece of anything
Middle English attome, from Latin atomus, from Greek atomos, indivisible, atom : a-, not; see a-1 + tomos, cutting (from temnein, to cut.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Old French atome, from Latin atomus ("smallest particle"), from Ancient Greek ἄτομος (atomos, "indivisible"), from ἀ- (a-, "not") + τέμνω (temnō, "I cut"). (Wiktionary)