What is Isotope?
1.
Each element has many versions that contain a different number of neutrons in the nucleas. Each different version of the element is called an isotope.
Carbon-13 is and isotope of Carbon
2.
Lighter and heavier versions of the same thing, (but usually in reference to atoms)
Bud and Bud Lite are "isotopes" of Bud. When you gain weight, you just become an "isotope" of your former self.
See