| Operation am offenen Herzen | open-heart surgery |
| Operationszeichen | operator |
| die Augen offen halten | keep an eye peeled |
| Operationsverstärker | op-amp |
| Separation of Concerns | separation of concerns |
| Person des öffentlichen Lebens | public figure |
| Person vom linken Flügel | left-winger |
| Person vom rechten Flügel | right-winger |
| personenbezogene Daten | personal data |
| Persona non grata | persona non grata |
| rationalisieren | rationalize |
| von ganzem Herzen | wholehearted |
| Dreck am Stecken haben | skeleton in the cupboard |
| jemandem am Herzen liegen | close to one's heart dear to one's heart near one's heart |
| Verzeih meine offene Rede | pardon my French |
| Tag der offenen Tür | open house open day |
| entkoffeinieren | decaffeinate |
| mit den Wölfen heulen | when in Rome, do as the Romans do |
| Metalle der Seltenen Erden | rare earth element |
| zerissenes Herz | broken heart |