There are multiple definitions:

1. oculi utrique(Latin)

   • both eyes
   • OD, OS
   • Ophthalmology

2. observation unit(English)

   • observation diagnoses that are most likely to require inpatient admission were hematochezia (60%), viral pneumonia (46%), and bronchiolitis (43%)
   • OS
   • Emergency medicine, Pediatrics, Triage
   • https://doi.org…/peds.2004-0391