n 1  :  any of two or more species of atoms of a chemical element with the same atomic number and position in the periodic table and nearly identical chemical behavior but with differing atomic mass or mass number and different physical properties  2  :  NUCLIDE iso*to*pic adj iso*to*pi*cal*ly adv iso*to*py n pl  -pies  
 
 
 
Similar sounding terms:  iso·type 
 
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