There are multiple definitions:

1. radio frequency(English)

   • Biophysics, Bioengineering
   • https://doi.org…OC.2014.2298437

2. rectus femoris(Latin)

   • a muscle
   • BF, GLM, GM, MGS, sEMG, SENIAM, ST, TA, VML, VMO, VI, VLL, VLO, VL, RF-s
   • Anatomy, Musculoskeletal system
   • https://doi.org…6/1476-5918-7-9
   • https://doi.org…0421-004-1199-x

3. releasing factor(English)

4. right frontal(English)

   • Brain (dys)function

5. rheumatic fever(English)

   • AF, MS
   • Rheumatology

6. Rosenthal fiber(English)

   • see astrocyte

7. regurgitant fraction(English)

   • FFV, EF, AR, AS, AVR, bSSFP, CE-MRA, CMR, LGE, LVESVi, LVOT, MAVD, PC, RVol, VENC, VHD
   • Cardiology, Ratio-based metric
   • https://doi.org…acc.2010.11.043

8. risk factor(English)

   • Risk factor, Scoring systems/scales, Statistics

9. residual fraction(English)

   • amount of blood remaining in the ventricle at end-systole compared to filling volume
   • EF, ESV, VAC
   • Cardiology, Hemodynamics, Ratio-based metric
   • https://doi.org…8703(51)90146-9

10. random forest(English)

    • ML, RF-SLAM
    • Machine learning

11. receptive field(English)

    • MIA
    • Electrophysiology, Pain
    • https://doi.org…8993(91)91601-v

12. rheumatoid factor(English)

    • polyreactive IgM antibody produced by a subset of B lymphocytes. Binds to the Fc portion of the IgG molecule
    • IgG, IgM
    • Rheumatology
    • https://doi.org…9517(10)37018-8

13. restrictive filling [pattern](English)

    • in DCM the LV distensibility is reduced because of increased intrinsic stiffness or decreased operating compliance, and LA pressure is increased. The elevated LA pressure results in an increased E velocity. The decrease in mid-to-late diastolic distensibility produces a more rapid transmitral pressure equilibration, creating a “dip-and-plateau” effect. This is characterized by short IVRT, high E velocity and short DT, and reduced A velocity. This pattern can be further stratified into “reversible” and “irreversible” subgroups with loading manipulations, resulting in incremental prognostic value
    • DCM, LA, LV, PN, DT, IVRT
    • Cardiology
    • https://doi.org…-3754-5.50026-3

14. repeated fasting/refeeding [cycle](English)

    • used to examine the neurobiological basis of bingeing-related eating disorders using an animal model system
    • MS, NH, NPY, PND
    • Adiposity, Nutrition, Experimental animal
    • https://doi.org…38/ijo.2008.108

15. reduced-fluence(English)

    • refers to photodynamic therapy
    • BCVA, CFT, CNV, IVR, mCNV, PDT, RFPDT
    • Ophthalmology
    • https://doi.org…0417-016-3498-4

16. relapsing fever(English)

    • ectoparasite-borne, tropical diseases caused by a group of related species of Borrelia, different from the Borrelia species responsible for the Lyme disease
    • Tropical medicine, Parasitology
    • https://doi.org…-4390-4.00075-8

17. replicative form(English)

    • ADV, ss
    • Virology
    • https://doi.org….1159/000149727

18. Rutherford stage(English)

    • IC, LEAD
    • Atherosclerosis /atherogenic, Vascular disease
    • https://doi.org…055/a-1916-9717

19. residue-free(English)

    • may refer to a tablet
    • ABPS, BBPS, CS, ELS, FPK, NaP, PEG, RF-NaP
    • Pharmacology / pharmaceutics
    • https://doi.org…41.2006.00776.x

20. regulatory factor(English)

    • RFX1, CD44
    • Regulation / control, Transcription
    • https://doi.org…3/neuonc/nou010

21. rod fracture(English)

    • AR, ASD, PJK
    • Spine (or spinal cord), Injury
    • https://doi.org…/ssrr.2022-0131