| jenonlyAdverb | Adverb |
| jenomonlyAdverb | Adverb |
| jeslenursery, crecheNoun | Noun |
| jestliif, whetherConjunction | Conjunction |
| ještěeven, still, again, yet, moreAdverb | Adverb |
| jetgo by vehicle; rideVerb | Verb |
| jevištěstageNoun | Noun |
| jezditgo by vehicle regularly; rideVerb | Verb |
| jezerolakeNoun | Noun |
| JežíšekježíšekBaby Jesus, Czech Christmas gift bringerNoun | Noun |
| jídelnacafeteria, dining roomNoun | Noun |
| jídelnídining; menuAdjective | Adjective |
| jídlofood, mealNoun | Noun |
| jihsouthNoun | Noun |
| jinakotherwise; differentlyAdverb | Adverb |
| jinamsomewhere elseAdverb | Adverb |
| jindeelsewhereAdverb | Adverb |
| jinýother; differentAdjective | Adjective |
| jísteatVerb | Verb |
| jistěcertainlyAdverb | Adverb |
| jistýsure; certainAdjective | Adjective |
| jítgo; walkVerb | Verb |
| jízdenkaticketNoun | Noun |
| jízdnítravel; ridingAdjective | Adjective |
| jižnísouthernAdjective | Adjective |
| jménonameNoun | Noun |
| jmenovat sebe called; be namedVerb | Verb |
| joyeahParticle | Particle |
| jógayogaNoun | Noun |
| jogurtyogurtNoun | Noun |
| JUDr.judr.Doctor of Law titleNoun | Noun |
| JugosláviejugoslávieYugoslaviaNoun | Noun |
| kto, towardPreposition | Preposition |
| kabátcoatNoun | Noun |
| kabelcableNoun | Noun |
| kabelkahandbagNoun | Noun |
| kabinkachanging roomNoun | Noun |
| kadeřnicehairdresserNoun | Noun |
| kadeřnictvíhair salonNoun | Noun |
| kadeřníkhairdresserNoun | Noun |
| kafecoffeeNoun | Noun |
| kachnaduckNoun | Noun |
| kakaococoaNoun | Noun |
| kalendářcalendarNoun | Noun |
| kalhotypantsNoun | Noun |
| kaloriecalorieNoun | Noun |
| kamwhereAdverb | Adverb |
| kamarádmale friendNoun | Noun |
| kamarádkafemale friendNoun | Noun |
| kámenstoneNoun | Noun |
| kamiontruck; lorryNoun | Noun |
| KanadakanadaCanadaNoun | Noun |
| KanaďankanaďanCanadian manNoun | Noun |
| KanaďankakanaďankaCanadian womanNoun | Noun |
| kanárcanaryNoun | Noun |
| kanárskýcanaryAdjective | Adjective |
| kancelářoffice; agencyNoun | Noun |
| kandidátcandidateNoun | Noun |
| kapelabandNoun | Noun |
| kapesníkhandkerchief; tissueNoun | Noun |
| kapitalismuscapitalismNoun | Noun |
| kapkadropNoun | Noun |
| kapkydrops; medicine dropsNoun | Noun |
| kaplechapelNoun | Noun |
| kaprcarpNoun | Noun |
| kapustasavoy cabbageNoun | Noun |
| karamelcaramelNoun | Noun |
| karavancaravan; camper vanNoun | Noun |
| kardiologcardiologistNoun | Noun |
| kartacardNoun | Noun |
| kartáčbrushNoun | Noun |
| kartáčektoothbrushNoun | Noun |
| kartycards; playing cardsNoun | Noun |
| kastrolsaucepan; potNoun | Noun |
| kašeporridge; mashNoun | Noun |
| kašelcoughNoun | Noun |
| kašlatcoughVerb | Verb |
| kašnafountainNoun | Noun |
| katedrálacathedralNoun | Noun |
| katolickýCatholicAdjective | Adjective |
| katoličkaCatholic womanNoun | Noun |
| katolíkCatholic manNoun | Noun |
| kávacoffeeNoun | Noun |
| kavárnacafeNoun | Noun |
| každodennídaily; everydayAdjective | Adjective |
| každopádněanywayAdverb | Adverb |
| každýeach, everyPronoun | Pronoun |
| kdewhereAdverb | Adverb |
| kdowhoPronoun | Pronoun |
| kdokolianyonePronoun | Pronoun |
| kdywhenAdverb | Adverb |
| kdybyifConjunction | Conjunction |
| kdysionce (in the past)Adverb | Adverb |
| kdyžwhenConjunction | Conjunction |
| kečupketchupNoun | Noun |
| kelímekcup; small containerNoun | Noun |
| kempcampsite; campNoun | Noun |
| keřbush; shrubNoun | Noun |
| kilokilogram; kiloNoun | Noun |
| kilogramkilogram; kiloNoun | Noun |