| prn | as required [Lat. pro re nata] |
|---|---|
| RDED | radiation dose required |
| T90 | time required for 90% mortality in a population of microorganisms exposed to a toxic agent |
| TD | the time required to double the number of cells in a given population; thermal death time |
| tG1 | the time required to complete the G1 phase of the cell cycle |