| Termen/ Term | Nr. apariții/ No. occurrences |
| OCTOCORAL | 4 |
| OCTOCORALIER | 28 |
| OCTOCORALIER GORGONAR | 2 |
| OCTOCORALLIER | 1 |
| OCTOPOD | 1 |
| ODOGACI | 2 |
| ODOLEAN | 10 |
| OFIURID | 17 |
| OFIUROID | 4 |
| OFIUROIDEU | 1 |
| OITA | 2 |
| OLUSCA | 1 |
| OM | 2 |
| OM ORGANIZATIA INTERNA EMBRION 7 LUNI | 1 |
| OM SCHELET EMBRION 5 LUNI | 1 |
| OMAG | 3 |
| OMIDA SI TUB DIGESTIV LA FLUTURE | 1 |
| ONICOFOR | 1 |
| OPAITA | 1 |
| OPAITA ROSIE | 2 |
| OPINTIC | 1 |
| OPINTICA | 1 |
| OPOSUMUL | 5 |
| OPOSUMUL CENUSIU | 1 |
| OPOSUMUL DE APA | 1 |
| ORANGUTAN | 1 |
| ORANGUTANUL | 4 |
| ORASTICA | 2 |
| ORBALT | 1 |
| ORBETE | 18 |
| ORBETELE MARE | 1 |
| ORBETELE MIC | 1 |
| ORESNITA | 3 |
| ORGAN INTERN | 9 |
| ORGAN UMAN | 7 |
| ORGANIZATIA INTERNA | 3 |
| ORGANIZATIA INTERNA LA BROASCA | 1 |
| ORGANIZATIA INTERNA LA BUHAI | 1 |
| ORGANIZATIA INTERNA LA CEGA | 1 |
| ORGANIZATIA INTERNA LA ECHIDNA | 1 |
| ORGANIZATIA INTERNA LA LIPITOARE | 1 |
| ORGANIZATIA INTERNA LA MELC | 1 |
| ORGANIZATIA INTERNA LA PASTRAV | 1 |
| ORGANIZATIA INTERNA LA RAC | 1 |
| ORGANIZATIA INTERNA LA SARPE | 1 |
| ORGANIZATIA INTERNA LA SOPIRLA | 2 |
| ORGANIZATIA INTERNA LA TESTOASA | 1 |
| ORNITORINCUL | 1 |
| ORYX | 1 |
| ORZ PADURET | 1 |