Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
density [ˈdɛnsɪtɪ] n (of population) (also PHYS) пло́тность f
single/double-density disk (COMPUT) диск с одина́рной/двойно́й пло́тностью
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.