| Abbreviation | Definition |
|---|---|
| NRC | Nuclear Regulatory Commission |
| NTCP | Normal Tissue Complication Probability |
| OAR | Off-Axis Ratio |
| ODI | Optical Distance Indicator |
| OER | Oxygen Enhancement Ratio |
| OF | Obliquity Factor |
| OHHAR | Occupational Health Hazard Assessment Report |
| OSL | Optically Stimulated Luminescence |
| PA | Postero-Anterior |
| PBU | Pressure Biofeedback Unit |
| PDD | Percentage Depth Dose |
| PDD(10) | Percentage Depth Dose at 10 cm depth in water |
| PDL | Pulsed Dye Laser |
| PDR | Pulsed Dose Rate |
| PE | Potential Energy |
| PET | Post-Exposure Treatment |
| POD | Physiologically Optimized Dosimeter |
| POE | Point Of Entry |
| POLIO | POLIOmyelitis |
| PP | Pair Production |