| oordning | Aufruhr |
| Oordning -en | Durcheinander |
| oorganiserad | unorganisiert |
| oorganisk | unorganisch |
| oorganisk förorening | anorganischer Schadstoff |
| oorganisk kemi | Anorganik |
| oorganiskt gödselmedel | Mineraldünger |
| oortodox | unorthodox |
| Oorts kometmoln | Oortsche Wolke |
| Oostende | Ostende |
| Opabinia | Opabinia |
| opaion | Auge |
| opak | lichtundurchlässig |
| opal | Opal |
| opalescens | Opalisieren |
| opalskimrande | opalisierend |
| opartisk | gerecht |
| opartiskhet | Unparteilichkeit |
| opassande | unverschämt |
| opassande beteende | Ungehörigkeit |
| opassande förslag | anstößiger Antrag |
| opasslig | marode |
| Opatija | Opatija |
| OPC | OLE for Process Control |
| OPEC | OPEC |
| Opel | Opel |
| Opel Antara | Opel Antara |
| Opel Corsa | Opel Corsa |
| Opel Frontera | Opel Frontera |
| Opel Meriva | Opel Meriva |
| Opel Senator | Opel Senator |
| Opel Vectra | Opel Vectra |
| Opel Zafira | Opel Zafira |
| Open Directory Project | Open Directory Project |
| Open Enterprise Server | Open Enterprise Server |
| Open Shortest Path First | Open Shortest Path First |
| Open Sound System | Open Sound System |
| Open Source Development Labs | Open Source Development Labs |
| Open Systems Interconnection | OSI-Modell |
| Open University | Open University |
| Open Water | Open Water |
| OpenArena | OpenArena |
| Openbox | Openbox |
| OpenSolaris | OpenSolaris |
| OPENSTEP | OpenStep |
| OpenSUSE | OpenSuse |
| OpenVMS | Virtual Memory System |
| OpenVPN | OpenVPN |
| opera | Oper |
| Opera -n | Oper |
| Opera buffa | Opera buffa |
| Opera metal | Symphonic Metal |
| opera- | Opern- |
| operabel | operabel |
| Operación Puerto | Dopingskandal Fuentes |
| Operaen på Holmen | Königliche Oper |
| Operahuset i Sydney | Sydney Opera House |
| operation | chirurgische Eingriff |
