There are multiple definitions:

1. American Osteopathic Association(English)

   • DO
   • Organizations (clinical)
   • https://osteopathic.org/

2. acute opname-afdeling(Dutch)

   • ACEP, EMS
   • Emergency medicine

3. American Optometric Association(English)

   • COA, COT
   • Organizations (documentation), Ophthalmology