| 3107 | obey |
| 253 | object |
| 2164 | objection |
| 1497 | objective |
| 2112 | obscure |
| 550 | observation |
| 1000 | observatory |
| 421 | observe |
| 1955 | obstacle |
| 778 | obtain |
| 756 | obvious |
| 302 | occur |
| 377 | ocean |
| 1591 | occupy |
| 1898 | occasion |
| 1913 | occasionally |
| 2692 | occupation |
| 1129 | odd |
| 2693 | odor |
| 240 | offer |
| 327 | official |
| 1156 | officer |
| 1481 | offspring |
| 2866 | offense |
| 263 | oil |
| 2428 | omit |
| 3088 | onion |
| 417 | operate |
| 619 | operation |
| 719 | optical |
| 847 | opportunity |
| 1024 | option |
| 1040 | oppose |
| 1170 | opposite |
| 1215 | opinion |
| 1634 | opposition |
| 1720 | opponent |
| 2015 | optimistic |
| 2599 | optimum |
