There are multiple definitions:

1. small for date(English)

   • SGA
   • Pregnancy, Neonatology

2. septum to free wall distance change(English)

   • PH, RVEF, TAAD, TAPSE
   • Cardiology, Medical imaging
   • https://doi.org…1532-429x-12-35

3. symptom-free day(English)

   • Asthma, Prognosis
   • https://doi.org…30079907x187982