Nuclei with same number of protons but different number of neutrons are called
Nuclei with same number of neutrons but different atomic number are called
Nuclei with same mass number are called
Nuclei with same number of protons (same atomic number) and different number of neutrons are called Isotopes. These nuclei belong to the same element as the atomic number remains the same.
Nuclei with same number of neutrons but different number of protons (different atomic number) are called isotones.
Nuclei with same mass number, that is, same "sum of neutrons and protons" are called isobars.