The S.I. unit of radioactivity, equal to one radioactive decay per second.
An Si-derived unit of activity of a radionuclide equal to the quantity of the material having one spontaneous nuclear transition, i.e., disintegrations, per second. One curie has 3.7 X 10¹⁰ transitions per second. Thus, one curie is equivalent to 3.7 X 10¹⁰ becquerels.