| 1 | English | observational | Relating to observation, especially scientific... |
| 2 | English | observation | The act of observing, and the fact of being... |
| 3 | French | observation | observation |
| 4 | Latin | observatio | watching, observing; observation, attention;... |
| 5 | Latin | observo | I observe, watch; I guard, keep watch over; I... |
| 6 | Latin | ob- | towards; against |
| 7 | Latin | obolus | obolus |
| 8 | Ancient Greek | ὀβολός | obol, obolus, used at Athens as both a weight and... |
| 9 | Ancient Greek | ὀβελός | a spit, rod; a horizontal line |
| 10 | Ancient Greek | βέλος | missile, arrow, dart; weapon; something quickly... |
| 11 | Proto-Indo-European | gʷélHos | — |
| 12 | Proto-Indo-European | gʷelH- | to throw, reach, pierce; to hit by throwing |