| optional | optional |
| Option | option |
| optimal | optimal optimum |
| national | national |
| rational | rational |
| Optimat | optimate |
| Rationale | rationale |
| Aktionär | shareholder stockholder |
| arational | arational |
| emotional | emotional sentimental |
| fiktional | fictional |
| regional | regional |
| atonal | atonal |
| tonal | tonal |
| epigonal | epigon |
| spinal | spinal |
| Koptin | Copt |
| Optimum | optimum |
| Optode | optode |
| Adoption | adoption affiliation |