1. (

• os ,

) a mouth or mouthlike opening ;

2. (

• osmium ,
• Os ,
• atomic_number_ ,

) a hard brittle blue-grey or blue-black metallic element that is one of the platinum metals; the heaviest metal known ;

3. (

• operating_system ,
• OS

) (computer science) software that controls the execution of computer programs and may provide various services ;

4. (

• oculus_sinister ,
• OS ,

) the left eye ;

5. (

• bone ,
• os

) rigid connective tissue that makes up the skeleton of vertebrates ;