There are multiple definitions:

1. outpatient department(English)

   • OP
   • Hospital admission

2. Orphan Products Development(English)

   • refers to developing treatments for inborn errors
   • FDA, IEM, ODA
   • Pharmacology / pharmaceutics
   • https://doi.org…gme.2003.10.015

3. Open Payments Database(English)

   • industry, academia, and professional societies provide financial and in-kind support for physician-lead research; however, the prevalence and role often remain unreported
   • COI, FD
   • Financial issues, Ethics
   • https://doi.org…fas.2022.01.029