| S & T | Science & Technology |
| SAARC | South Asian Association for Regional Cooperation |
| SACA | Special Agreement on Commodity Arrangements |
| SACU | Southern African Customs Union |
| SADC | Southern African Development Community |
| SAFTA | South America Free Trade Area |
| SAFTA | South Asia Free Trade Area |
| SAP | Structural Adjustment Programme |
| SAPTA | South Asia Preferential Trade Area |
| SBA | Strategic business alliance |
| SBCD | Second Banking Coordination Directive (European Community) |
| SCM | Subsidies and countervailing measures |
| SCU | Sectoral customs union |
| S & D | Special and differential (treatment) |
| SEA | Single European Act |
| SEE | State economic enterprise |
| SELA | Sistema Económico Latinamericano (Latin american Economic System) |
| SEM | Single European Market |
| SFTA | Sectoral free trade area |
| SICA | Sistema de la Integración Centroamericana |
| SIECA | (Permanent) Secretariat of the General Treaty on Central American Economic Integration |
| SII | Structural Impediments Initiative |
| SIIC | Standard International Trade Classification |
| SMC | Singapore Ministerial Conference |
| SME | Small and Medium Enterprise |
| SOM | Senior Officials' Meeting (APEC) |
| SSOM | Special Senior Officials' Meeting (APEC) |
| SPARTECA | South Pacific Regional Trade and Economic Cooperation Agreement |
| SPF | South Pacific Forum |
| SPM | Sanitary and Phytosanitary Measures |
| SPS | Sanitary and Phytosanitary (measures) |
| SREZ | Sub-regional economic zone |
| SSG | Special safeguard |
| SSP | Special safeguard provisions |
| STA | Semi conductor Trade Agreement |
| STA | Short-term Arrangement Regarding International Trade in Cotton Textiles |
| STABEX | (System for the) Stabilisation of Export Earnings (European Community) |
| STE | State-trading enterprise |
| STM | Simply-transformed manufacture |
| STO | State trading Organization |
| STR | Special Trade Representative |
| SYSMIN | System for the Promotion of Mineral Production and Exports (European Community) |