| NLM | National Library of Medicine; noise level monitor |
|---|---|
| NNI | noise and number index |
| NR | do not repeat [Lat. non repetatur]; nerve root; neural retina; neutral red; noise reduction; nonreac... |
| NTD | neural tube defect; nitroblue tetrazolium dye; noise tone difference; 5'-nucleotidase |
| PN | papillary necrosis; parenteral nutrition; penicillin; perceived noise; percussion note; periarteriti... |