| Abbreviation | Definition |
|---|---|
| SIMU | Simulations Plus, Inc. |
| SIMU | Simulations Plus, Incorporated (de-listed) |
| SIMU | Simulations Plus, Incorporated (de-listed) |
| SINA | SINA Corporation |
| SINCE | Southland Financial, Inc. |
| SINCE | Southland Financial, Incorporated (de-listed) |
| SINX | Sionix Corporation |
| SIORE | Superior Oil & Gas Company |
| SIPCP | Sierra Pacific Power Company |
| SIPX | S I P E X Corporation |
| SIRI | Sirius Satellite Radio |
| SIRKE | Sierra Rockies Corporation |
| SIRT | Sierra National Bank of Tehachapi |
| SIRT | Sierra National Bank of Tehachapi (de-listed) |
| SIRT | Sierra National Bank of Tehachapi (de-listed) |
| SISG | I S G International Software Group, LTD. |
| SISI | S I Technologies, Inc. |
| SISKE | Siskon Gold Corporation |
| SITE | SiteOne Landscape Supply, Incorporated |
| SITE | Spectrasite Holdings, Inc. |