For a specified isotope, or mixture of isotope, the activity of a material divided by the mass of the material.
PAC, 1994, 66, 2513. (Nomenclature for radioanalytical chemistry (IUPAC Recommendations 1994)
) on page 2515 [Terms
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)
) on page 993 [Terms