There are multiple definitions:

1. free induction decay(English)

   • PR, MRI
   • Medical imaging
   • https://doi.org…BC.2015.7318383

2. functional iron deficiency(English)

   • HFpEF
   • Cardiology, Clinical chemistry, Erythrocyte

3. flicker-light-induced vasodilation(English)

   • refers to retinal arterioles
   • FMD
   • Hemodynamics
   • https://doi.org…1002/ehf2.14483

4. frequency–intensity–duration(English)

   • these curves provide practical, easy and clear representation of intensity variation through fitted exponential curves with coefficient of determination that is almost equal to 1 (R2 ˜ 1). FID curves are drawn on semilogarithmic paper with rainfall intensity estimations from the convenient Gamma probability distribution functions or cumulative distribution functions
   • CDF, PDF
   • Statistics
   • https://doi.org…1111/jfr3.12229

5. flame ionization detector(English)

   • CCK, CD36, ENaC, FAT, FCI, FFA, FFQ, FNS, FPD, GCCR, gLMS, GPCR, GPR120, LIPK, LIPM, LIPN, MAP, NEFA, ORN, SAFA
   • Clinical chemistry, Nutrition
   • https://doi.org…srev.00061.2021

6. focus-to-image distance(English)

   • AGD, HVL, ICRP, 2ABD
   • Radiotherapy /radiation
   • https://doi.org…1747-017-0026-1