| Oktopus | octopus |
| Oktober | October |
| Oktogon | octagon |
| Oktole | octuplet |
| Topas | topaz |
| Topos | topos |
| Tropus | trope |
| Ödipus | Oedipus |
| Korpus | corpus body base |
| Typus | type |
| Doktorat | doctorate |
| Doktorin | Doctor |
| Oktagon | octagon |
| Oktal- | octal |
| Oktant | Octans |
| Oktonion | octonion |
| Doktor | doctor physican |
| Oktaeder | octahedron |
| Oktave | octave octonion Cayley algebra Cayley numbers |
| Oktett | octet |