Is it farther or further?


[ahy-suh-tohp] /ˈaɪ səˌtoʊp/
noun, Chemistry
any of two or more forms of a chemical element, having the same number of protons in the nucleus, or the same atomic number, but having different numbers of neutrons in the nucleus, or different atomic weights. There are 275 isotopes of the 81 stable elements, in addition to over 800 radioactive isotopes, and every element has known isotopic forms. Isotopes of a single element possess almost identical properties.
1910-15; iso- + -tope < Greek tópos place
Related forms
[ahy-suh-top-ik] /ˌaɪ səˈtɒp ɪk/ (Show IPA),
isotopically, adverb Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for isotopes
  • isotopes are versions of an element that have almost the same chemical properties but different atomic weights.
  • But the world has a short attention span, whereas the half-lives of many radioactive isotopes are long indeed.
  • isotopes can even indicate the order in which the planets formed.
  • Oxygen isotopes from drinking water, for example, become fixed in people's teeth as they age.
  • Infinitesimal radioactive isotopes can be carried along on the breeze, landing unseen on the ground, clothes and skin.
  • It is highly unstable, and all isotopes are radioactive.
  • Those isotopes with short half-lives have already disappeared.
  • Primarily a research reactor, it also produces medical isotopes.
  • Water contains two isotopes of oxygen, one of which has two more neutrons than the other, making it heavier.
  • Breeder reactors are possible because of the proportion of uranium isotopes that exist in nature.
British Dictionary definitions for isotopes


one of two or more atoms with the same atomic number that contain different numbers of neutrons
Derived Forms
isotopic (ˌaɪsəˈtɒpɪk) adjective
isotopically, adverb
isotopy (aɪˈsɒtəpɪ) noun
Word Origin
C20: from iso- + Greek topos place
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
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Word Origin and History for isotopes



1913, literally "having the same place," introduced by British chemist Frederick Soddy (1877-1956) on suggestion of Margaret Todd, from Greek isos "equal" (see iso-) + topos "place" (see topos); so called because despite the different atomic weights, the various forms of an element occupy the same place on the periodic table.

Online Etymology Dictionary, © 2010 Douglas Harper
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isotopes in Medicine

isotope i·so·tope (ī'sə-tōp')
One of two or more atoms having the same atomic number but different mass numbers.

i'so·top'ic (-tŏp'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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isotopes in Science
One of two or more atoms that have the same atomic number (the same number of protons) but a different number of neutrons. Carbon 12, the most common form of carbon, has six protons and six neutrons, whereas carbon 14 has six protons and eight neutrons. Isotopes of a given element typically behave alike chemically. With the exception of hydrogen, elements found on Earth generally have the same number of protons and neutrons; heavier and lighter isotopes (with more or fewer neutrons) are often unstable and undergo radioactive decay.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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isotopes in Culture
isotope [(eye-suh-tohp)]

In physics, different forms of the same element, with nuclei that have the same number of protons but different numbers of neutrons. Isotopes are distinguished from each other by giving the combined number of protons and neutrons in the nucleus. For example, uranium 235 is the isotope of uranium that has 235 protons and neutrons in its nucleus rather than the more commonly occurring 238. All elements have isotopes.

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Slang definitions & phrases for isotopes

in the trenches

adverb phrase

In the workplace; in contact with the people or problems in a situation; unprotected by distance or illusion: I needed to be back in the trenches where I could really relate to a community/More retrospective accounts are elegant and noble. Watson told it like it was in the trenches (1970s+)

The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D.
Copyright (C) 2007 by HarperCollins Publishers.
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