| Abbreviation | Definition |
|---|---|
| M | Mega |
| M | Mercury |
| m | Meter |
| M | Middle |
| M | Million |
| M | Missing (Data) |
| M | Missing data |
| M | Monitor |
| M | Monitor (MON preferred) |
| M | Number of Revolutions Required for the Rendezvous |
| M- | Time in Days Before Move Operations |
| M&C | Maintenance and Checkout |
| M&C | Monitor and Control Panel |
| M&F | Materials and Facilities |
| M&M | Materials and Maintenance |
| M&O | Maintenance and Operations |
| M&P | Materials and Processes |
| M&P | Materials and Processing |
| M&R | Maintenance and Refurbishment |
| M&RF | Maintenance and Refurbishing Facility |