| S/D ratio | Systolic / Diastolic ratio |
|---|---|
| C/N | carbon/nitrogen [ratio]; carrier/ noise [ratio] |
| DR | degeneration reaction; delivery room; deoxyribose; diabetic retinopathy; diagnostic radiology; digit... |
| ER | efficiency ratio; epigastric region; ejection rate; electroresection; emergency room; endoplasmic re... |
| L/P | lactate/pyruvate [ratio]; liver plasma [concentration]; lymph/plasma [ratio] |