In radiobiology, the<unk>  (often abbreviated as<unk>  is the ratio of biological<unk>  of one type of ionizing radiation<unk>  to another, given the same amount of absorbed energy. The<unk>  is an empirical value that varies depending on the type of ionizing radiation, the energies involved, the biological effects being considered such as cell death, and the oxygen tension of the tissues or so-called oxygen effect.
Relative biological effectiveness
Biological plausibility
Therapeutic index
Effective dose 
Equivalent dose
Risk–benefit ratio
Appropriate use criteria
Maximum acceptable toxicant concentration