Here's why:

* Isotope refers to a specific type of atom. It's not a state of being, but a classification.

* Atoms are the fundamental building blocks of matter. They consist of protons, neutrons, and electrons.

* Isotopes are atoms of the same element (meaning they have the same number of protons) but with different numbers of neutrons.

To be considered an isotope, an atom must have a different number of neutrons than other atoms of the same element.

For example:

* Carbon-12 and Carbon-14 are both isotopes of carbon. They both have 6 protons (defining them as carbon), but Carbon-12 has 6 neutrons, while Carbon-14 has 8 neutrons.

Let me know if you'd like more examples or have any other questions about isotopes!