isotope
noun
iso·tope
ˈī-sə-ˌtōp 
1
: any of two or more species of atoms of a chemical element with the same atomic number and nearly identical chemical behavior but with differing atomic mass or mass number and different physical properties
2
: nuclide
Examples of isotope in a Sentence
Recent Examples on the Web
Russia also denied poisoning Alexander Litvinenko, a former Russian agent turned Kremlin critic who died in London in 2006 after ingesting the radioactive isotope polonium-210.
—
Jill Lawless, Los Angeles Times, 14 Feb. 2026
In the new work, Milton and her colleagues examined the ratio of different isotopes—forms of atoms with differing numbers of uncharged neutrons in their nucleus—of carbon, nitrogen and sulfur in maize cobs archaeologists had uncovered from the Chincha Valley.
—Meghan Bartels, Scientific American, 11 Feb. 2026
While working on Copernicus, York was the first researcher to find an isotope of hydrogen known as deuterium inside these clouds.
—Bob Goldsborough, Chicago Tribune, 7 Feb. 2026
There are a series of unstable, radioactive ruthenium isotopes believed to have a triaxial shape, similar to an almond or coffee bean, according to a press release.
—Prabhat Ranjan Mishra, Interesting Engineering, 2 Feb. 2026
See All Example Sentences for isotope
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Jill Lawless, Los Angeles Times, 14 Feb. 2026
In the new work, Milton and her colleagues examined the ratio of different isotopes—forms of atoms with differing numbers of uncharged neutrons in their nucleus—of carbon, nitrogen and sulfur in maize cobs archaeologists had uncovered from the Chincha Valley.
—Meghan Bartels, Scientific American, 11 Feb. 2026
While working on Copernicus, York was the first researcher to find an isotope of hydrogen known as deuterium inside these clouds.
—Bob Goldsborough, Chicago Tribune, 7 Feb. 2026
There are a series of unstable, radioactive ruthenium isotopes believed to have a triaxial shape, similar to an almond or coffee bean, according to a press release.
—Prabhat Ranjan Mishra, Interesting Engineering, 2 Feb. 2026
See All Example Sentences for isotope
Cite this Entry
“Isotope.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/isotope. Accessed 22 Feb. 2026.
Copy CitationKids Definition
isotope
noun
iso·tope
ˈī-sə-ˌtōp
: any of the forms of an element that differ in the number of neutrons in an atom
Medical Definition
isotope
noun
iso·tope
ˈī-sə-ˌtōp
1
: any of two or more species of atoms of a chemical element with the same atomic number and position in the periodic table and nearly identical chemical behavior but with differing atomic mass or mass number and different physical properties
2
: nuclide
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