| OR | a logical binary relation that is true if any argument is true, and false otherwise; [o]estrogen rec... |
|---|---|
| ORD | optical rotatory dispersion; oral radiation death |
| PAR | participating provider; passive avoidance reaction; perennial allergic rhinitis; photosynthetically ... |
| PQRST | provocative and palliative factors, quality of pain, radiation of pain, severity of pain, timing of ... |
| PWBRT | prophylactic whole brain radiation therapy |