| NRS | neurobehavioral rating scale; normal rabbit serum; normal reference serum; numerical rating scale |
|---|---|
| NRSCC | National Reference System in Clinical Chemistry |
| ORS | olfactory reference syndrome; oral rehydration solution; oral surgery, oral surgeon; Orthopaedic Res... |
| OSI | open systems interconnection [reference model] |
| PDR | pediatric radiology; peripheral diabetic retinopathy; Physicians' Desk Reference; postdelivery room;... |