| Abbreviation | Definition |
|---|---|
| MTDS | Middle Tennessee Daffodil Society |
| MTESZ | Federation of Technical and Scientific Societies |
| MTESZ | Mszaki s Termszettudomnyi Egyesletek Szvetsge |
| MTESZ | Müszaki és Természettudományi Egyesületek Szövetsége |
| MTHS | Middle Tennessee Hosta Society |
| MTHS | Middletown Township Historical Society |
| MTHS | Mountain Top Historical Society |
| MTMS | Music Theory and Musicology Society |
| MTPS | Merseyside Tramway Preservation Society |
| MTTS | Microwave Theory and Techniques Society |
| MVHS | Minnesota Valley Humane Society |
| MVRS | Mystic Valley Railway Society |
| MWAS | Mid Western Artifact Society |
| MWSA | Military Writer's Society of America |
| NA | Norsk Arkivråd |
| NA | Norsk Arkivrd |
| NA | Norwegian Archives Council |
| NAACLT | North American Association for Celtic Language Teachers |
| NAARS | North American Araucania Royalist Society |
| NAARS | North Arkansas Amateur Radio Society |