| Orca | Orka |
| orchestra | orkester |
| orchid | orhideja |
| Orchidaceae | Kukavičevke |
| Ordeliness | Red |
| order | ukaz |
| Order of Alexander Nevsky | Red Aleksandra Nevskega |
| Order of Bogdan Khmelnitsky | Red Bogdana Hmeljnickega |
| Order of Christ | Templjarji |
| Order of Friars Minor Capuchin | Frančiškani |
| Order of Friendship of Peoples | Red prijateljstva med narodi |
| Order of Glory | Red slave |
| Order of Kutuzov | Red Kutuzova |
| Order of Lenin | Red Lenina |
| Order of Nakhimov | Red Nakimova |
| Order of Santiago | Santiago |
| Order of Suvorov | Red Suvorova |
| Order of the National Hero | Narodni heroj |
| Order of the October Revolution | Red oktobrske revolucije |
| Order of the Patriotic War | Red domovinske vojne |
| Order of the Red Banner | Red rdeče zastave |
| Order of the Red Banner of Labour | Red rdeče delavske zastave |
| Order of the Red Star | Red rdeče zvezde |
| Order of Ushakov | Red Ušakova |
| Order of Victory | Red zmage |
| Order relation | Relacija urejenosti |
| Order theory | Relacija urejenosti |
| Orders of magnitude | Red velikosti |
| Ordet | Beseda |
| Ordinal numbers | Ordinalno število |
| ordinance | predpis |
| Ordinary people | Narod |
| Ordo | Red |
| Ordovician | Ordovicij |
| ore | ruda |
| Orebić | Orebić |
| Oregano | Navadna dobra misel |
| Oregon | Oregon |
| Oregon Territory | Oregon |
| organ | organ |
| Organ player | Orglavec |
| organelle | organel |
| organic carbon | organski ogljik |
| organic chemistry | organska kemija |
| organic farming | organsko kmetijstvo |
| Organic manure | Gnojilo |
| organic matter | organska snov |
| organic nitrogen | organski dušik |
| Organic nomenclature | Znanstvena klasifikacija |
| organic pollutant | organsko onesnaževalo |
| organic pollution | organsko onesnaženje |
| organic solvent | organsko topilo |
| organic substance | organska snov |
| organic waste | organski odpadki |
| organisation | organizacija |
| Organisation for Economic Co-operation and Development | Organizacija za gospodarsko sodelovanje in razvoj |
| organisation of teaching | izobraževalna organizacija |
| organisation of the legal system | organiziranost pravnega sistema |
| Organisation Todt | Organizacija Todt |
| organism | organizem |
| Organizatio | Entiteta |
| Organization | Organizacija |
| Organization for Security and Co-operation in Europe | Organizacija za varnost in sodelovanje v Evropi |
| Organization of American States | Organizacija ameriških držav |
| Organizational memory | Spomin |
| organochlorine compound | organoklorova spojina |
| organohalogen compound | organohalogena spojina |
| organoleptic property | organoleptična lastnost |
| organometallic compound | organokovinska spojina |
| organonitrogen compound | organodušikova spojina |
| organooxygen compound | organokisikova spojina |
| organophosphorous compound | organofosforjeva spojina |
| organosulphur compound | organožveplova spojina |
| orgasm | orgazem |
| Orhan Pamuk | Orhan Pamuk |
| Orichalcum | Med |
| Orient | Vzhod |
| Oriental Orthodoxy | Pravoslavje |
