| SHMO, S/HMO | social health maintenance organization |
|---|---|
| SI | International System of Units [Fr. le Systeme International d'Unites]; sacroiliac; saline infusion; ... |
| SIS | semantic indexing system; serotinin irritation syndrome; simian sarcoma; simulator-induced syndrome;... |
| SocSec | Social Security |
| SocServ | social services |