decay rate

of a radioactive material
https://doi.org/10.1351/goldbook.D01542
See: activity (of a radioactive material)
Source:
PAC, 1994, 66, 2513. 'Nomenclature for radioanalytical chemistry (IUPAC Recommendations 1994)' on page 2518 (https://doi.org/10.1351/pac199466122513)