| Abbreviation | Definition |
|---|---|
| SWP | Safe Working Pressure |
| SWR | Standing Wave Ratio |
| SWS | SWitch Scan |
| SWT | Science Working Team |
| SWT | Supersonic Wind Tunnel |
| SXA | Single-energy X-ray Analysis |
| SXC | Soft X-ray Camera |
| SXP | Solar X-ray Photometer |
| SXS | Soft X-Ray Spectrometer |
| SXT | Sextant |
| SXT | Soft X-ray Telescope |
| SY | Shoulder Yaw |
| SY | System |
| SYM | Symbol |
| SYMM | Symmetrical |
| SYN | SYNchronous |
| SYN | SYNthetic |
| SYNC | Synchronize |
| SYNCOM | Hughes Spin Stabilized Spacecraft |
| SYNCOM | Synchronous Communication Satellite (Hughes) |