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ion
ionnounan electrically charged atom or group of atoms formed by the loss or gain of one or more electrons, as a cation positive ion, which is created by electron loss and is attracted to the cathode in electrolysis, or as an anion negative ion, which is created by an electron gain and is attracted to the anode. The valence of an ion is equal to the number of electrons lost or gained and is indicated by a plus sign for cations and a minus sign for anions, thus: Na + , Cl−, Ca ++ , S = .
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Ion
Ionnounthe eponymous ancestor of the Ionians: a son of Apollo and Creusa who is abandoned by his mother but returns to become an attendant in Apollo's temple at Delphi.
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-ion
-iona suffix, appearing in words of Latin origin, denoting action or condition, used in Latin and in English to form nouns from stems of Latin adjectives (communion; union ), verbs (legion; opinion ), and especially past participles (allusion; creation; fusion; notion; torsion ).
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Ion.
Ion.abbreviationIonic.
ion
1 Americannoun
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ions
plural
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an electrically charged atom or group of atoms formed by the loss or gain of one or more electrons, as a cation positive ion, which is created by electron loss and is attracted to the cathode in electrolysis, or as an anion negative ion, which is created by an electron gain and is attracted to the anode. The valence of an ion is equal to the number of electrons lost or gained and is indicated by a plus sign for cations and a minus sign for anions, thus: Na + , Cl−, Ca ++ , S = .
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one of the electrically charged particles formed in a gas by electric discharge or the like.
noun
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Classical Mythology. the eponymous ancestor of the Ionians: a son of Apollo and Creusa who is abandoned by his mother but returns to become an attendant in Apollo's temple at Delphi.
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(italics) a drama on this subject (415? b.c.) by Euripides.
abbreviation
noun
suffix
Other Word Forms
Noun Inflected Forms
Etymology
Origin of ion1
< Greek ión going, neuter present participle of iénai to go; term introduced by Michael Faraday in 1834
Origin of -ion3
< Latin -iōn- (stem of -iō ) suffix forming nouns, especially on past participle stems; replacing Middle English -ioun < Anglo-French < Latin -iōn-
Explanation
An ion is an atom or particle with a positive or negative electrical charge. Think of an ion as having a plus or minus sign. Ion is a word you are most likely to encounter in a physics or chemistry text. But you don’t have to be a chemist or physicist to understand the concept. If you had a neutral particle and you were able to remove or add an electron, then you would have an ion — a charged particle. Don't confuse the tiny ion with the similar word eon, which is an extremely long period of time.
Vocabulary lists containing ion
Electricity and Magnetism - Introductory
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Structure and Properties of Matter - Middle School
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The ACT Science Test: Chemistry Review 1
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
Karl Deisseroth, Peter Hegemann and Georg Nagel were honored for their research into “light-gated ion channels and optogenetics.”
From Science Daily ● Oct. 19, 2026
Instead of searching for quark and antiquark pairs after lead ion collisions, the researchers looked for events in which one quark traveled through the plasma in nearly the opposite direction from a "Z boson."
From Science Daily ● Oct. 6, 2026
To examine the samples, the researchers used focused ion beam preparation, transmission electron microscopy, and chemical analysis.
From Science Daily ● Oct. 3, 2026
Sodium ion batteries have got energy storage experts excited because they could end up much cheaper to build and operate than lithium ion.
From BBC ● Sep. 29, 2026
"But we wouldn't lose Hermes. We can remotely operate it. So long as the reactor and ion engines continued to work, we could bring it back."
From "The Martian" by Andy Weir
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The group’s alleged leader, Constantin Ion, aka Piranha, was charged but not arrested.
From The Wall Street Journal ● Sep. 20, 2026
"We are in a new era here, similar to 70-odd years ago," said Frank Nerling, a Jefferson Lab collaborator from Germany's GSI Helmholtz Centre for Heavy Ion Research and Goethe University Frankfurt.
From Science Daily ● Sep. 2, 2026
Ion is tailored for procedures in the lung, typically to sample suspicious nodules or legions as part of a cancer diagnosis.
From Barron's ● Apr. 21, 2026
Games will also air on Ion and USA Network.
From Los Angeles Times ● Mar. 18, 2026
“It is time we sent for Prince Aegon as well,” Lord Ion announced.
From "A Dance with Dragons" by George R. R. Martin
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In the first place, the Portuguese, who discovered that island in 1506, and explored its coasts in the following years, could not have Ion. remained in ignorance of De Gonneville's voyage.
From The History of Australian Exploration from 1788 to 1888 by Ernest Favenc
During an electrochemical reaction, hydrogen ions, also known as protons, can be produced or consumed at the electrodes.
From Science Daily ● Oct. 12, 2026
In these experiments, heavy ions such as lead are accelerated to nearly the speed of light and smashed together.
From Science Daily ● Oct. 6, 2026
To build the simulation, the researchers encoded a string breaking model into a chain of 13 trapped ions.
From Science Daily ● Sep. 26, 2026
Metal ions help transfer energy from a star's radiation into surrounding material, pushing that material outward.
From Science Daily ● Sep. 24, 2026
Thus, under physiological conditions, there would always be positively charged ions like sodium or magnesium lying nearby to neutralize the negatively charged phosphate groups.
From "Double Helix" by James D. Watson
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Get a wordDefinitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.