Noun

• S: (n) os (a mouth or mouthlike opening)
• S: (n) osmium, Os, atomic number 76 (a hard brittle blue-grey or blue-black metallic element that is one of the platinum metals; the heaviest metal known)
• S: (n) operating system, OS ((computer science) software that controls the execution of computer programs and may provide various services)
• S: (n) oculus sinister, OS (the left eye)
• S: (n) bone, os (rigid connective tissue that makes up the skeleton of vertebrates)