| ICTV | International Committee for the Taxonomy of Viruses |
|---|---|
| IWGMT | International Working Group on Mycobacterial Taxonomy |
| L/N | letter/numerical [system] |
| NA | Avogadro constant or number; nalidixic acid; Narcotics Anonymous; network administrator; neuraminida... |
| NRS | neurobehavioral rating scale; normal rabbit serum; normal reference serum; numerical rating scale |