| Orthoklas | orthoclase |
| Ortolan | ortolan |
| Osteoklast | osteoclast |
| Orthogon | rectangle |
| Kortholt | kortholt |
| Orthoepie | orthoepy |
| Orthofoto | orthophoto |
| Orthoptist | orthoptist |
| Orthopäde | orthopedist orthopaedist orthopaedic specialist orthopedic specialist orthopedic surgeon |
| ortho- | ortho- |
| orthodox | orthodox |
| orthognath | orthognathic orthognathous |
| orthogonal | orthogonal |
| Tholos | tholos |
| Thomas | Thomas |
| Sophokles | Sophocles |
| Patroklos | Patroclus |
| Autoklav | autoclave |
| Thekla | Thecla |
| Orthodoxie | Orthodoxy |