| S-IgA | secretory immunoglobulin A |
|---|---|
| S-MUAP | surface-detected motor unit action potential |
| S-NSE | serum neuron-specific enolase |
| S-OCT | serum ornithine carbamyl transferase |
| S-R | smooth-rough [bacteria] |
| S-T | [segment] in electrocardiography, the portion of the segment between the end of the S wave and the beginning of the T wave; sickle-cell thalassemia |