radioactivity
noun [ U ] uk/ˌreɪ.di.əʊ.ækˈtɪv.ə.ti/ us/ˌreɪ.di.oʊ.ækˈtɪv.ə.t̬i/
放射（性）
the quality that some atoms have of producing a type of energy that can be very harmful to health
放射线；辐射线；辐射能
the energy produced by atoms in this way
A dangerous amount of radioactivity was released into the environment last month. 上个月泄漏了大量的放射线，造成很大危险。