There are multiple definitions:

1. relative abundance distribution(English)

   • Statistics

2. renal artery denervation(English)

   • see refractive hypertension
   • RAAS
   • Hypertension

3. right atrial [transverse] dimension(English)

   • RA, LAD
   • Cardiology, Medical imaging
   • https://doi.org…aoms.2010.14469

4. residual angle deformity(English)

   • used to evaluate the effectiveness of tibial fracture repair
   • RDD, AP, TSF
   • Orthopedics, Surgery, Medical imaging
   • https://doi.org…891-022-05112-3