Pronunciation: (īn'stīn; Ger. īn'shtīn"),[key] —n. 1. Al•bert Pronunciation: (al'burt; Ger. äl'bert),[key] 1879–1955, German physicist, U.S. citizen from 1940: formulator of the theory of relativity; Nobel prize 1921.
2. Al•fred Pronunciation: (al'frid; Ger. äl'fret),[key] 1880–1952, German musicologist in U.S.
3. (l.c.) Physics,Chem.a unit of radiant energy, equal to the energy of radiation that is capable of photochemically changing one mol of a photosensitive substance.