This is my understanding so far:
Average atomic mass is the mass of an element considering isotopes and is measured in atomic mass units. However relative atomic mass is the average mass of an atom ( Considering isotopes ) relative to carbon 12. As a result, relative atomic mass possesses no units. The same is applied to atomic mass which is the mass of an atom ( Isotope ) measured in atomic mass units. Relative isotopic mass is the mass of an isotope relative to carbon 12 and also possesses no units. Is this understanding completly correct?
Furthermore, I was wondering about Atomic mass units. If this measures the actual mass of an atom for example then how is it that relative mass gives the same result just without the unit. Is atomic mass units somehow related to carbon 12 as well?