| odpovědní listanswer sheetWord combination | Word combination |
| odpovídatanswer; answer regularlyVerb | Verb |
| odskočit sileave for a momentPhrase | Phrase |
| odtáhnoutpull away; tow awayVerb | Verb |
| odtamtudfrom thereAdverb | Adverb |
| odtudfrom hereAdverb | Adverb |
| odvážnýbrave; boldAdjective | Adjective |
| odvéstlead away; take awayVerb | Verb |
| odvézttake away by vehicle; drive awayVerb | Verb |
| ohlásitreport; announce; registerVerb | Verb |
| ohňostrojfireworks displayNoun | Noun |
| ohodnocenívaluationNoun | Noun |
| oholit seshave oneselfVerb | Verb |
| ochotawillingnessNoun | Noun |
| ochranaprotectionNoun | Noun |
| ochutnattaste; try food or drinkVerb | Verb |
| ochutnávattaste; sample repeatedlyVerb | Verb |
| ojetýused; worn (esp. car)Adjective | Adjective |
| okamžitěimmediatelyAdverb | Adverb |
| oknowindowNoun | Noun |
| okoeyeNoun | Noun |
| okolísurroundingsNoun | Noun |
| okopírovatcopyVerb | Verb |
| okresnídistrictAdjective | Adjective |
| okupaceoccupationNoun | Noun |
| okurkacucumberNoun | Noun |
| okurkovýcucumberAdjective | Adjective |
| olejoilNoun | Noun |
| olovoleadNoun | Noun |
| olympiádaOlympicsNoun | Noun |
| omáčkasauceNoun | Noun |
| omezené ručenílimited liabilityWord combination | Word combination |
| omezenýlimited; restrictedAdjective | Adjective |
| omlouvám seI'm sorry; excuse mePhrase | Phrase |
| omlouvat seapologise; apologizeVerb | Verb |
| omluvit seapologiseVerb | Verb |
| omylmistakeNoun | Noun |
| onhePronoun | Pronoun |
| onashePronoun | Pronoun |
| opačnýoppositeAdjective | Adjective |
| opakovatrepeatVerb | Verb |
| opalovánítanningNoun | Noun |
| opalovat sesuntanVerb | Verb |
| operaoperaNoun | Noun |
| operaceoperationNoun | Noun |
| operetaoperettaNoun | Noun |
| operovatoperate; perform surgeryVerb | Verb |
| opicemonkeyNoun | Noun |
| opičkalittle monkeyNoun | Noun |
| opilýdrunkAdjective | Adjective |
| opozičníoppositionAdjective | Adjective |
| opravarepairNoun | Noun |
| opravářrepairmanNoun | Noun |
| opravdovýrealAdjective | Adjective |
| opravdureally, trulyAdverb | Adverb |
| opravitcorrect; fix; repairVerb | Verb |
| opravnarepair shopNoun | Noun |
| opravna obuvishoe repair shopWord combination | Word combination |
| opravna oděvůclothing repair shopWord combination | Word combination |
| opravovatfix; repair; correctVerb | Verb |
| optikaoptician shopNoun | Noun |
| optimistaoptimistNoun | Noun |
| optimistickýoptimisticAdjective | Adjective |
| optimistkafemale optimistNoun | Noun |
| oranžovýorangeAdjective | Adjective |
| ordinacedoctor's officeNoun | Noun |
| ordinačníconsulting-room; office-hoursAdjective | Adjective |
| ordinační hodinydoctor's office hoursWord combination | Word combination |
| ordinovatsee patients; prescribeVerb | Verb |
| organizaceorganizationNoun | Noun |
| organizátororganizerNoun | Noun |
| organizovatorganizeVerb | Verb |
| orchestrorchestraNoun | Noun |
| orientaceorientationNoun | Noun |
| orientačníapproximate; orientationalAdjective | Adjective |
| origináloriginalNoun | Noun |
| originálníoriginalAdjective | Adjective |
| orlicefemale eagleNoun | Noun |
| oslavacelebrationNoun | Noun |
| oslavitcelebrateVerb | Verb |
| oslovovataddress; speak toVerb | Verb |
| osmeightNumber | Number |
| osmažitfry lightly; fryVerb | Verb |
| osmdesáteightyNumber | Number |
| osmdesátá létathe eighties; the 1980sPhrase | Phrase |
| osmnácteighteenNumber | Number |
| osmnáctýeighteenthNumber | Number |
| osobapersonNoun | Noun |
| osobněpersonally, in personAdverb | Adverb |
| osobnípersonalAdjective | Adjective |
| osobní dokladidentity documentWord combination | Word combination |
| osobnostpersonalityNoun | Noun |
| osprchovat setake a showerVerb | Verb |
| ostatníotherAdjective | Adjective |
| ostrovislandNoun | Noun |
| ostrýsharp; spicyAdjective | Adjective |
| ostříhatcut hair; trimVerb | Verb |
| ostýchavýshyAdjective | Adjective |
| OSVČosvčself-employed personWord combination | Word combination |
| ošetřittreat; attend toVerb | Verb |