, or os
may refer to: ▪ Austrian Airlines ▪ O.S., a notation for alumni of the ancient Jesuit public school, Stonyhurst College ▪ O.S. Engines, a Japanese manufacturer of model aircraft engines ▪ Ocean Science
, an oceanographic journal published by the European Geosciences Union ▪ Oculus sinister
, meaning "left eye" in eyeglass prescriptions ▪ Ohtahara syndrome, a brain disorder ▪ Old Style date, indicating the Julian Calendar, as opposed to "N.S." indicating from the Gregorian Calendar ▪ On-sight climbing, the ascent of a rock climbing route on the first attempt, with no falls, without prior knowledge of its specifics beyond its difficulty rating and number of protection points ▪ Open source, a software development model ▪ Operating system, a software that manages the hardware and software of a computer ▪ Order of Santiago, Spanish order dedicated to St James the Greater ▪ Ordinary Seaman, an unlicensed member of the deck department of a merchant ship ▪ Ordnance Sergeant, an enlisted rank in the U.S.