| 1 | Ancient Greek | ὀρθός | straight, upright, erect; straight forward, in a... |
| 2 | Proto-Hellenic | ortʰwós | — |
| 3 | Proto-Indo-European | h₃r̥dʰwós | — |
| 4 | Proto-Indo-European | h₃erdʰ- | to increase, grow; upright, high |
| 5 | Proto-Indo-European | -wós | Creates adjectives from verb stems |