| SIF | serum-inhibition factor |
|---|---|
| SIFT | selector ion flow tube |
| SIG | small inducible gene |
| sig | sigmoidoscopy; significant |
| SIg, sIg | surface immunoglobulin |
| SIGH-D | structured interview for the Hamilton Depression Scale |
| sigmo | sigmoidoscope or sigmoidoscopy |
| SIH | stimulation-induced hypalgesia; stress-induced hyperthermia; suction-induced hypoxemia |
| SIHE | spontaneous intramural hematoma of the esophagus |
| SII | self-inflicted injury |