| Kooperation | cooperation co-operation |
| Kooperative | cooperative |
| kooperativ | cooperative |
| Kooptation | co-optation co-option |
| Operation | surgery operation |
| Komparation | comparison |
| Föderation | federation |
| Konföderation | confederation |
| Moderation | moderation presentation |
| Konsekration | dedication |
| Konspiration | conspiracy |
| Kompensation | compensation |
| Konversation | conversation |
| Kopulation | copulation |
| Korrelation | correlation association |
| unkooperativ | intransigent |
| Koordination | coordination |
| kooperieren | co-operate |
| Herzoperation | heart surgery |
| Operator | operator administrator |