| Acronym | Definition |
|---|
| SIN | Special Item Number (lists GSA contractor service and/or product requirements) |
| SIN | Social Insurance Number (Canada) |
| SIN | Sine |
| SIN | Sinus |
| SIN | Sir Isaac Newton |
| SIN | Strength in Numbers |
| SIN | Sistema Interligado Nacional (Portuguese: National Interconnected System, Brazil) |
| SIN | Safety In Numbers |
| SIN | Silicon Nitride |
| SIN | Substitute It Now (International Chemical Secretariat) |
| SIN | Special Item Number |
| SIN | Social Insurance Number |
| SIN | Serial in |
| SIN | Servicio de Inteligencia Nacional (Spanish: National Intelligence Service; Peru) |
| SIN | Servicio de Impuestos Nacionales (Spanish: National Tax Service; Bolivia) |
| SIN | Società Italiana di Nefrologia |
| SIN | Scientific Information Network |
| SIN | Sinaloa (Estado de) (México) |
| SIN | Società Italiana di Neurologia |
| SIN | Spanish International Network |
| SIN | Shadow in the Night (song) |
| SIN | Northern Sinai (Egyptian automobile license plate) |
| SIN | Speech in Noise (audiology) |
| SIN | Servicio de Inteligencia Naval (Spanish: Naval Intelligence Service; Argentina and Chile) |
| SIN | Securities Industry News |
| SIN | Shadaloo Intimidation Network (gaming) |
| SIN | Satan's Identification Number |
| SIN | Singapore, Singapore - Changi International Airport (Airport Code) |
| SIN | Stop Islam Now |
| SIN | South Australian Sex Industry Network |
| SIN | Self Inflicted Nonsense |
| SIN | Status Indicator Normal (telecommunications) |
| SIN | Superconductor-Insulator-Normal Metal (aka Normal Metal-Insulator-Superconductor) |
| SIN | Substance Identification Number (United Nations) |
| SIN | Service Identification Number |
| SIN | Service Interruption Notification (various organizations) |
| SIN | Scottish Islands Network |
| SIN | Status Indication Normal Alignment (SS7) |
| SIN | Self-Implementation Notice |
| SIN | Synthetic Infant Nutrition (formula) |
| SIN | System Identification Network |
| SIN | Support Information Network |
| SIN | Self Induced Negativity |
| SIN | Scwerezeresches Institut für Nuklearforschung (Switzerland) |
| SIN | Study Item Number |
| SIN | Stock Inventory Number |
| SIN | Standard Inventory Number |
| SIN | Spherically Integrated Nearfield |