Atomic Mass Unit
Also called a.m.u. and dalton, and designated with the symbol "u". A unit of mass equal to 1/12 the mass of an unbound carbon-12 nucleus that is at rest and in its ground state. This is:
1 u = 1.660538782×10-27 kilograms = 931.494027 MeV/c2
The measurement is convenient because it is approximately equal to the mass of one hydrogen atom, and in general because any atom's mass in atomic mass units is approximately equal to the number of protons and neutrons it contains. The dalton and the kilodalton are important units of measurement in chemistry, biochemistry, and nanotechnology.