| Abbreviation | Definition |
|---|---|
| SI | sinus irregularities |
| SI | situs inversus |
| SI | smoking index |
| SI | snoring index |
| SI | social interaction |
| SI | spinal injury |
| SI | stratum intermedium |
| SI | stress incontinence |
| SI | stroke index |
| SI | Structured Interview |
| SI | suicidal ideation |
| SI | superior/inferior |
| SI | survival index |
| SI | systolic index |
| SIA | sequence independent amplification |
| SIA | sequential injection technique |
| SIA | serum inhibitory activity |
| SIA | serum-in-agar |
| SIA | sialic acid |
| SIA | slide immunoenzymatic assay |