Difference between relative atomic mass and atomic mass unit?

Relative atomic mass is a synonym for atomic weight. It is defined as the weighted mean of the atomic masses of all the atoms of a chemical element found in a particular sample, weighted by isotopic abundance. Whereas, Atomic mass unit (amu) is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of 1.66053892 × 10^?27 kg.

Relative atomic masses are expressed in atomic mass units.