| OPEC | OPEC |
| Opel | Opel |
| Opel Antara | Opel Antara |
| Opel Corsa | Opel Corsa |
| Opel Frontera | Opel Frontera |
| Opel Meriva | Opel Meriva |
| Opel Vectra | Opel Vectra |
| Opel Zafira | Opel Zafira |
| Open content | Freie Inhalte |
| Open di Francia | French Open |
| Open Directory Project | Open Directory Project |
| Open Gaming License | Open Gaming License |
| Open reading frame | Offener Leserahmen |
| Open Shortest Path First | Open Shortest Path First |
| Open Sound System | Open Sound System |
| Open source | Open Source |
| Open Source Definition | Open Source Definition |
| Open Space Technology | Open Space |
| Open Systems Interconnection | OSI-Modell |
| Open Unified Process | Open Unified Process |
| Open Water | Open Water |
| OpenArena | OpenArena |
| OpenCms | OpenCms |
| OpenDocument Format Alliance | Open Document Format Alliance |
| OpenLaszlo | OpenLaszlo |
| OpenNap | OpenNap |
| OpenPGP | OpenPGP |
| OpenSolaris | OpenSolaris |
| Opensource | Open Source |
| OpenSUSE | OpenSuse |
| OpenVMS | Virtual Memory System |
| OpenVPN | OpenVPN |
| OpenWRT | OpenWrt |
| opera | Stück |
| opera a puntate | Serie |
| Opera buffa | Opera buffa |
| Opera cinese | Chinesische Oper |
| opera d'arte | Kunststück |
| Opera dei Pupi | Sizilianisches Marionettentheater |
| Opera derivata | Bearbeitung |
| opera di bene | Hilfswerk |
| opera di carità | Hilfswerk |
| opera di consultazione | Nachschlagewerk |
| Opera di Pechino | Peking-Oper |
| opera di riassetto dopo una catastrofe | Katastrophenaufräumung |
| opera lirica | Oper |
| Opera Nazionale Balilla | Balilla |
| opera pia | Hilfswerk |
| Opera rock | Rockoper |
| Opera semiseria | Opera semiseria |
| Opera seria | Opera seria |
| Opera Software | Opera Software |
| operabile | operabel |
| Operación Puerto | Dopingskandal Fuentes |
| operai | Arbeitskraft |
| operaia | Arbeitskraft |
| operaia edile | Bauarbeiterin |
| operaia metallurgica | Metallarbeiterin |
| operaia montatrice | Installateurin |
| operaio | Arbeitskraft |
| operaio edile | Bauarbeiter |
| operaio metallurgico | Metallarbeiter |
| operaio montatore | Installateur |
| operare | handeln |
| Operare in borsa su informazioni riservate | Insiderhandel |
