| Abbreviation | Definition |
|---|---|
| SI | Système International d'unités (International System of Units) |
| SID | Shallow, Intermediate, and Deep |
| SIDAAC | Snow and Ice Distributed Active Archive Center |
| SIDMED | Siderúrgica de Mediterráneo |
| SIFT | Short-term Inundation Forecasting of Tsunamis project |
| SIGRID | Format For The Archiving And Exchange Of Digital Sea-ice Data |
| SIGRID | Sea-Ice GRID |
| SIMI | Sea Ice Mechanics Initiative |
| SIMS | Stable Isotope Mass Spectrometer |
| SIO | Scripps Institution of Oceanography |
| SIO | Skidaway Institute of Oceanography |
| SIR | Shuttle Imaging Radar |
| SISEX | Satellite Imaging Spectrometer Experiment |
| SITAR | Seafloor Imaging And Toxicity Assessment Of Risks |
| SITE | Space Influences on the Terrestrial Environment |
| S-K | Saltonstall- Kennedy Promote and Develop American Fisheries Bill |
| S-K | Saltonstall-Kennedy Promote and Develop American Fisheries Bill |
| SKW | Super Kamehame Wave |
| SLAM | Scuba Lifesaving and Accident Management |
| SLAM | Simultaneous Localization and Mapping |