See also: Appendix:Variations of "os"
- (countable, computing) Initialism of .
- (calendar systems) Abbreviation of .
- (eyewear) Initialism of ; (the left eye from the patient's point of view)
- (eyewear): O.D.
O.S. m (indeclinable)
- (Can we verify(+) this sense?) (eyewear) O.S. (“oculus sinister”) (the left eye from the patient's point of view)