Dictionary.com
definitions

radioisotope

[rey-dee-oh-ahy-suh-tohp]

noun

a radioactive isotope, usually artificially produced: used in physical and biological research, therapeutics, etc.

Origin of radioisotope

First recorded in 1940–45; radio- + isotope
Related formsra·di·o·i·so·top·ic [rey-dee-oh-ahy-suh-top-ik] /ˌreɪ di oʊˌaɪ səˈtɒp ɪk/, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for radioisotope

radioisotope

noun

an isotope that is radioactive
Derived Formsradioisotopic (ˌreɪdɪəʊˌaɪsəˈtɒpɪk), adjective
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
Word Origin and History for radioisotope
n.

1946, from radio-, comb. form of radiation, + isotope.

Online Etymology Dictionary, © 2010 Douglas Harper
radioisotope in Medicine

radioisotope

[rā′dē-ō-ī′sə-tōp′]

n.

A naturally or artificially produced radioactive isotope.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
radioisotope in Science

radioisotope

[rā′dē-ō-ī′sə-tōp′]

A radioactive isotope of a chemical element. Carbon 14 and radon 222 are examples of naturally occurring radioactive isotopes.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.