| Abbreviation | Designation | |
|---|---|---|
| CH-SO | Solothurn, Kanton Solothurn (German) Canton of Solothurn | country code |
| s.o. | státní organizace (Czech) state organisation | organization |
| SO | Soest (German) | fare point / vehicle registration plate |
| Sö | Södertälje (Swedish) | station code |
| So | Solna (Swedish) | station code |
| SO | Chemins de fer de la Suisse Occidentale (France) | railway company |