| oktroyiert | forced upon imposed |
| oktroyieren | impose force |
| Oktober | October |
| kontrolliert | controlled certified checked |
| okkupiert | occupied |
| oxytoniert | oxytonize |
| tradiert | legacy |
| aktiviert | activated |
| kariert | chequered checked checkered |
| Oktonion | octonion |
| doktorieren | doctor |
| Oktaeder | octahedron |
| Oktett | octet |
| Oktole | octuplet |
| Oktologie | octology |
| Baktrier | Bactrian |
| ektropisch | ectropic |
| Controller | controller |
| Introsort | introspective sort |
| Tröster | comforter |