1. noun /ˈaɪ.sə.təʊp,ˈaɪ.sə.toʊp/
Any of two or more forms of an element where the atoms have the same number of protons, but a different number of neutrons within their nuclei. As a consequence, atoms for the same isotope will have the same atomic number but a different mass number (atomic weight).
2. verb /ˈaɪ.sə.təʊp,ˈaɪ.sə.toʊp/
See Also: homotope
Wikipedia foundation.