There are multiple definitions:

1. active forward elevation(English)

   • AER, RSA
   • Shoulder and other joints
   • https://doi.org…ses.2019.06.003

2. area of fitting ellipse(English)

   • CGM, CONGA, CSII, GV, MSE, PCP, SFE, SPCA
   • Diabetes, Insulin, Variability / oscillation, Monitoring
   • https://doi.org…phys.2018.01257

3. active front end(English)

   • a controllable rectifier. Its advantages include bidirectional power exchange between AC and DC and the feed of reusable power back to the mains
   • AC, DC, ESS, HEV
   • Energy transition
   • https://ieeexpl…rnumber=9337910