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Welcome to Lesson 27 of the Latinum Institute Czech Language Course. This lesson teaches the fundamental interrogative and relative pronoun co /tsɔ/, meaning “what.” This pronoun is essential for forming questions in Czech and appears constantly in everyday speech.
Unlike English, Czech distinguishes sharply between “who” (kdo) for persons and “what” (co) for things, objects, events, and ideas. The pronoun “co” also has case forms that change depending on its grammatical function in the sentence.
For the complete course index, visit: https://latinum.substack.com/p/index
Frequently Asked Question: What does “co” mean in Czech? “Co” is the Czech interrogative pronoun meaning “what.” It is used to ask about things, objects, events, and abstract concepts. It functions both as a question word (Co to je? - What is that?) and as a relative pronoun (To, co jsem viděl - That which I saw).
In this lesson, you will see “co” used in its various case forms across 30 example sentences, progressing from simple questions to complex constructions.
Key Takeaways: -
“Co” is the interrogative/relative pronoun for non-persons (use “kdo” for people) -
It declines through seven Czech cases: co, čeho, čemu, co, co, o čem, čím -
It triggers neuter singular agreement in verbs and adjectives -
It forms the basis for indefinite pronouns: něco (something), nic (nothing), cokoli (anything) -
Mastering “co” is essential for asking questions and forming complex sentences
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The interrogative pronoun “co” changes form according to the seven Czech cases. Here are the forms presented without a table:
Nominative (Who/what? - subject): co /tsɔ/
Genitive (Of whom/what? - possession): čeho /ˈtʃɛɦɔ/
Dative (To whom/what? - indirect object): čemu /ˈtʃɛmu/
Accusative (Whom/what? - direct object): co /tsɔ/
Vocative (Direct address): co /tsɔ/
Locative (About whom/what? - with prepositions): čem /tʃɛm/ (used with o, na, po, při, v)
Instrumental (With whom/what? - means/accompaniment): čím /tʃiːm/
Note: These case questions (koho? čeho? komu? čemu? etc.) are used by Czech speakers to determine which case a noun should take.
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27.1a Co to je? 27.1b Co (tsɔ) what to (tɔ) that/it je (jɛ) is
27.2a Co děláš? 27.2b Co (tsɔ) what děláš (ˈɟɛlaːʃ) do-you-2SG
27.3a Co je nového? 27.3b Co (tsɔ) what je (jɛ) is nového (ˈnɔvɛːɦɔ) new-GEN.SG.NEUT
27.4a Co si přeješ? 27.4b Co (tsɔ) what si (sɪ) REFL přeješ (ˈpr̝̊ɛjɛʃ) wish-you-2SG
27.5a Co to znamená? 27.5b Co (tsɔ) what to (tɔ) that/it znamená (ˈznamɛnaː) means
27.6a Co čteš? 27.6b Co (tsɔ) what čteš (tʃtɛʃ) read-you-2SG
27.7a Čeho se bojíš? 27.7b Čeho (ˈtʃɛɦɔ) of-what-GEN se (sɛ) REFL bojíš (ˈbɔjiːʃ) fear-you-2SG
27.8a Čemu nerozumíš? 27.8b Čemu (ˈtʃɛmu) to-what-DAT nerozumíš (ˈnɛrɔzumiːʃ) not-understand-you-2SG
27.9a O čem přemýšlíš? 27.9b O (ɔ) about čem (tʃɛm) what-LOC přemýšlíš (ˈpr̝̊ɛmiːʃliːʃ) think-you-2SG
27.10a Čím píšeš? 27.10b Čím (tʃiːm) with-what-INST píšeš (ˈpiːʃɛʃ) write-you-2SG
27.11a Co tam bylo? 27.11b Co (tsɔ) what tam (tam) there bylo (ˈbɪlɔ) was-NEUT.SG
27.12a Co jsi viděl? 27.12b Co (tsɔ) what jsi (jsɪ) AUX-you viděl (ˈvɪɟɛl) seen-MASC.SG
27.13a Nevím, co říct. 27.13b Nevím (ˈnɛviːm) not-know-I co (tsɔ) what říct (r̝̊iːtst) to-say
27.14a To je přesně to, co potřebuji. 27.14b To (tɔ) that je (jɛ) is přesně (ˈpr̝̊ɛsnɛ) exactly to (tɔ) that co (tsɔ) what/which potřebuji (ˈpɔtr̝̊ɛbʊjɪ) need-I
27.15a Co by se stalo, kdybych odešel? 27.15b Co (tsɔ) what by (bɪ) COND se (sɛ) REFL stalo (ˈstalɔ) happened-NEUT kdybych (ˈɡdɪbɪx) if-I odešel (ˈɔɟɛʃɛl) left-MASC.SG
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27.1 Co to je? → “What is that?”
27.2 Co děláš? → “What are you doing?”
27.3 Co je nového? → “What’s new?”
27.4 Co si přeješ? → “What do you wish for?”
27.5 Co to znamená? → “What does that mean?”
27.6 Co čteš? → “What are you reading?”
27.7 Čeho se bojíš? → “What are you afraid of?”
27.8 Čemu nerozumíš? → “What don’t you understand?”
27.9 O čem přemýšlíš? → “What are you thinking about?”
27.10 Čím píšeš? → “What are you writing with?”
27.11 Co tam bylo? → “What was there?”
27.12 Co jsi viděl? → “What did you see?”
27.13 Nevím, co říct. → “I don’t know what to say.”
27.14 To je přesně to, co potřebuji. → “That is exactly what I need.”
27.15 Co by se stalo, kdybych odešel? → “What would happen if I left?”
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27.1 Co to je?
27.2 Co děláš?
27.3 Co je nového?
27.4 Co si přeješ?
27.5 Co to znamená?
27.6 Co čteš?
27.7 Čeho se bojíš?
27.8 Čemu nerozumíš?
27.9 O čem přemýšlíš?
27.10 Čím píšeš?
27.11 Co tam bylo?
27.12 Co jsi viděl?
27.13 Nevím, co říct.
27.14 To je přesně to, co potřebuji.
27.15 Co by se stalo, kdybych odešel?
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These are the grammar rules for “co” in Czech:
The Case System and “Co”
The pronoun “co” changes form according to the seven Czech grammatical cases. The nominative and accusative forms are identical (co), but other cases show distinct forms:
The nominative (co) is used when “what” is the subject of the sentence: “Co se stalo?” (What happened?). The accusative (also co) marks the direct object: “Co vidíš?” (What do you see?).
The genitive (čeho) expresses “of what” and appears after certain verbs and prepositions that govern the genitive case. The verb “bát se” (to fear) takes the genitive, hence “Čeho se bojíš?” (What are you afraid of?).
The dative (čemu) means “to what” and is used with verbs requiring a dative object. The verb “rozumět” (to understand) takes the dative: “Čemu nerozumíš?” (What don’t you understand?).
The locative (čem) must be used with prepositions such as o (about), na (on), v (in), po (after), and při (during). Note that the preposition always precedes the locative form: “O čem mluvíš?” (What are you talking about?).
The instrumental (čím) indicates means or instrument: “Čím to otevřeš?” (What will you open it with?).
Agreement with “Co”
When “co” is the subject, the verb takes neuter singular form. Compare:
Kdo tam byl? (Who was there?) - “byl” is masculine singular because “kdo” is grammatically masculine.
Co tam bylo? (What was there?) - “bylo” is neuter singular because “co” is grammatically neuter.
“Co” as a Relative Pronoun
Besides its interrogative function, “co” serves as a relative pronoun meaning “which” or “that which”:
To, co říkáš, je pravda. (That which you say is true.)
Všechno, co vím, je od tebe. (Everything that I know is from you.)
Compounds with “Co”
Several important pronouns derive from “co”:
něco (something) - formed with the prefix ně- nic (nothing) - the negative form cokoli / cokoliv (anything, whatever) - the universal/indefinite form lecco (many things, various things) kdeco (all sorts of things)
Common Mistake to Avoid
English speakers sometimes use “co” when asking about people. Remember: use “kdo” (who) for persons and “co” for things, objects, events, and abstract concepts.
Incorrect: Co je tvůj bratr? (using “co” for a person) Correct: Kdo je tvůj bratr? (Who is your brother?)
However, when asking about someone’s profession or role, “co” can be used: Co je tvůj bratr? can mean “What is your brother?” (i.e., what does he do for work) - though this construction is informal.
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Historical and Cultural Background
The interrogative pronoun “co” is one of the most frequently used words in spoken Czech. It appears in countless everyday expressions and serves as a conversational filler similar to English “what?” or “huh?”
Register and Formality
In casual speech, “co” often appears in informal expressions:
“No co?” - “So what?” / “And?” “A co?” - “What about it?” “Co to má být?” - “What’s that supposed to be?”
These expressions carry a slightly confrontational or dismissive tone and should be used carefully in formal contexts.
Regional Variations
In Moravian dialects (eastern Czech Republic), you may hear “co” pronounced with slightly different intonation patterns. The standard Bohemian pronunciation /tsɔ/ remains the norm in formal Czech.
Idiomatic Expressions Using “Co”
“Co oči nevidí, to srdce nebolí.” - What the eyes don’t see, the heart doesn’t grieve over. (Out of sight, out of mind.)
“Co můžeš udělat dnes, neodkládej na zítra.” - What you can do today, don’t put off until tomorrow.
“Co na srdci, to na jazyku.” - What’s on the heart is on the tongue. (To speak one’s mind.)
“Za co, pane Bože?” - “What for, Lord?” (An expression of exasperation or suffering.)
Czech Literary Tradition
Czech literature is renowned for its philosophical depth and dark humor. Major authors include Karel Čapek, who invented the word “robot” in his 1920 play R.U.R.; Milan Kundera, author of The Unbearable Lightness of Being; Jaroslav Hašek, who wrote the satirical masterpiece The Good Soldier Švejk; and Bohumil Hrabal, known for Closely Observed Trains. Their works frequently employ questions beginning with “co” to explore existential themes.
This lesson is designed for English speakers learning Czech.
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The following passage comes from Karel Čapek’s R.U.R. (Rossum’s Universal Robots), the 1920 play that introduced the word “robot” to world languages.
Part F-A: Interlinear Text
Helena: Co jste to udělali? Co (tsɔ) what jste (jstɛ) AUX-you-PL to (tɔ) that udělali (ˈʊɟɛlalɪ) done-PL
Dr. Gall: Já nevím, co mám říct. Já (jaː) I nevím (ˈnɛviːm) not-know-I co (tsɔ) what mám (maːm) have-I/should-I říct (r̝̊iːtst) to-say
Helena: Co bude s námi? Co (tsɔ) what bude (ˈbʊdɛ) will-be s (s) with námi (ˈnaːmɪ) us-INST
Part F-B: Natural Text and Translation
Helena: Co jste to udělali? → “What have you done?”
Dr. Gall: Já nevím, co mám říct. → “I don’t know what to say.”
Helena: Co bude s námi? → “What will become of us?”
Part F-C: Original Czech Text
Helena: Co jste to udělali? Dr. Gall: Já nevím, co mám říct. Helena: Co bude s námi?
Part F-D: Grammar Commentary
This exchange demonstrates several uses of “co”:
In “Co jste to udělali?” the pronoun “co” serves as the direct object (accusative), asking about the action that was performed. The word order places the question word first, followed by the auxiliary “jste” and the demonstrative “to” for emphasis.
In “nevím, co mám říct,” “co” functions as a relative pronoun introducing a subordinate clause. The construction “co mám říct” (literally “what I should say”) uses the infinitive “říct” with the modal meaning of “mám.”
In “Co bude s námi?” the nominative “co” asks about the subject (what will be), while “s námi” (with us) uses the instrumental case after the preposition “s.”
Karel Čapek’s dramatic dialogue uses simple, direct questions to heighten tension. The repetition of “co” across these lines creates a mounting sense of crisis as the characters confront the consequences of creating artificial life.
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This dialogue presents a conversation between two friends meeting at a Prague coffee house, using “co” in natural conversational contexts.
Part A: Interlinear Construed Text
27.16a Ahoj! Co si dáš? 27.16b Ahoj (ˈaɦɔj) hello Co (tsɔ) what si (sɪ) REFL dáš (daːʃ) will-have-you-2SG
27.17a Nevím, co bych chtěl. 27.17b Nevím (ˈnɛviːm) not-know-I co (tsɔ) what bych (bɪx) COND-I chtěl (ˈxtjɛl) wanted-MASC.SG
27.18a Co takhle káva? 27.18b Co (tsɔ) what takhle (ˈtaxlɛ) how-about káva (ˈkaːva) coffee
27.19a Dobrý nápad. A co ty? 27.19b Dobrý (ˈdɔbriː) good nápad (ˈnaːpat) idea A (a) and co (tsɔ) what ty (tɪ) you
27.20a Já si dám čaj. Co je nového v práci? 27.20b Já (jaː) I si (sɪ) REFL dám (daːm) will-have-I čaj (tʃaj) tea Co (tsɔ) what je (jɛ) is nového (ˈnɔvɛːɦɔ) new-GEN v (v) in práci (ˈpraːtsɪ) work-LOC
27.21a Nic moc. A co tvoje rodina? 27.21b Nic (ɲɪts) nothing moc (mɔts) much A (a) and co (tsɔ) what tvoje (ˈtvɔjɛ) your rodina (ˈrɔɟɪna) family
27.22a Děti nevědí, co chtějí dělat v létě. 27.22b Děti (ˈɟɛcɪ) children nevědí (ˈnɛvjɛɟiː) not-know-they co (tsɔ) what chtějí (ˈxtjɛjiː) want-they dělat (ˈɟɛlat) to-do v (v) in létě (ˈleːcɛ) summer-LOC
27.23a To znám. Čeho se bojí tvůj syn? 27.23b To (tɔ) that znám (znaːm) know-I Čeho (ˈtʃɛɦɔ) of-what-GEN se (sɛ) REFL bojí (ˈbɔjiː) fears-he tvůj (tvuːj) your syn (sɪn) son
27.24a Bojí se toho, čemu nerozumí. 27.24b Bojí (ˈbɔjiː) fears-he se (sɛ) REFL toho (ˈtɔɦɔ) that-GEN čemu (ˈtʃɛmu) what-DAT nerozumí (ˈnɛrɔzumiː) not-understands-he
27.25a A čím se teď zabývá? 27.25b A (a) and čím (tʃiːm) with-what-INST se (sɛ) REFL teď (tɛc) now zabývá (ˈzabiːvaː) occupies-he
27.26a O čem bychom měli mluvit s učiteli? 27.26b O (ɔ) about čem (tʃɛm) what-LOC bychom (ˈbɪxɔm) COND-we měli (ˈmɲɛlɪ) should-PL mluvit (ˈmlʊvɪt) to-speak s (s) with učiteli (ˈʊtʃɪtɛlɪ) teachers-INST
27.27a Nevím, co bych vám poradil. 27.27b Nevím (ˈnɛviːm) not-know-I co (tsɔ) what bych (bɪx) COND-I vám (vaːm) you-DAT poradil (ˈpɔraɟɪl) advised-MASC.SG
27.28a Co si myslíš o nové kavárně na rohu? 27.28b Co (tsɔ) what si (sɪ) REFL myslíš (ˈmɪsliːʃ) think-you-2SG o (ɔ) about nové (ˈnɔvɛː) new-LOC kavárně (ˈkavaːrnɛ) coffee-house-LOC na (na) on rohu (ˈrɔɦʊ) corner-LOC
27.29a Je pěkná. To je přesně to, co Praha potřebuje. 27.29b Je (jɛ) is pěkná (ˈpjɛknaː) nice-FEM To (tɔ) that je (jɛ) is přesně (ˈpr̝̊ɛsnɛ) exactly to (tɔ) that co (tsɔ) what Praha (ˈpraɦa) Prague potřebuje (ˈpɔtr̝̊ɛbʊjɛ) needs
27.30a Tak co, půjdeme tam příště? 27.30b Tak (tak) so co (tsɔ) what půjdeme (ˈpuːjɟɛmɛ) will-go-we tam (tam) there příště (ˈpr̝̊iːʃcɛ) next-time
Part B: Natural Sentences
27.16 Ahoj! Co si dáš? → “Hello! What will you have?”
27.17 Nevím, co bych chtěl. → “I don’t know what I would like.”
27.18 Co takhle káva? → “How about coffee?”
27.19 Dobrý nápad. A co ty? → “Good idea. And what about you?”
27.20 Já si dám čaj. Co je nového v práci? → “I’ll have tea. What’s new at work?”
27.21 Nic moc. A co tvoje rodina? → “Not much. And what about your family?”
27.22 Děti nevědí, co chtějí dělat v létě. → “The children don’t know what they want to do in summer.”
27.23 To znám. Čeho se bojí tvůj syn? → “I know that feeling. What is your son afraid of?”
27.24 Bojí se toho, čemu nerozumí. → “He’s afraid of what he doesn’t understand.”
27.25 A čím se teď zabývá? → “And what is he occupied with now?”
27.26 O čem bychom měli mluvit s učiteli? → “What should we talk about with the teachers?”
27.27 Nevím, co bych vám poradil. → “I don’t know what I would advise you.”
27.28 Co si myslíš o nové kavárně na rohu? → “What do you think about the new coffee house on the corner?”
27.29 Je pěkná. To je přesně to, co Praha potřebuje. → “It’s nice. That’s exactly what Prague needs.”
27.30 Tak co, půjdeme tam příště? → “So, shall we go there next time?”
Part C: Czech Text Only
27.16 Ahoj! Co si dáš?
27.17 Nevím, co bych chtěl.
27.18 Co takhle káva?
27.19 Dobrý nápad. A co ty?
27.20 Já si dám čaj. Co je nového v práci?
27.21 Nic moc. A co tvoje rodina?
27.22 Děti nevědí, co chtějí dělat v létě.
27.23 To znám. Čeho se bojí tvůj syn?
27.24 Bojí se toho, čemu nerozumí.
27.25 A čím se teď zabývá?
27.26 O čem bychom měli mluvit s učiteli?
27.27 Nevím, co bych vám poradil.
27.28 Co si myslíš o nové kavárně na rohu?
27.29 Je pěkná. To je přesně to, co Praha potřebuje.
27.30 Tak co, půjdeme tam příště?
Part D: Grammar Notes for Genre Section
This dialogue showcases the full range of “co” usage in natural conversation:
Nominative/Accusative co: “Co si dáš?” (27.16), “Co je nového?” (27.20), “A co ty?” (27.19) - these show “co” as the most common question starter.
Genitive čeho: “Čeho se bojí...?” (27.23) - the verb “bát se” (to fear) requires the genitive case for its object.
Dative čemu: “čemu nerozumí” (27.24) - the verb “rozumět” (to understand) takes the dative case.
Locative čem: “O čem bychom měli mluvit” (27.26) - the preposition “o” (about) requires the locative case.
Instrumental čím: “čím se zabývá” (27.25) - the reflexive verb “zabývat se” (to occupy oneself with) takes the instrumental case.
Relative pronoun co: “to, co Praha potřebuje” (27.29) - “co” as a relative pronoun connecting clauses.
Colloquial expressions: “Tak co” (27.30) is an informal conversation marker meaning “so then” or “well then.”
Notice the conditional construction “co bych chtěl” (27.17) and “co bych vám poradil” (27.27), where “co” introduces a dependent clause with the conditional mood.
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The Pronunciation of “Co” /tsɔ/
The Czech letter “c” is always pronounced /ts/, similar to the “ts” in English “cats.” Never pronounce it as /k/ or /s/ alone. The vowel “o” is short and open, similar to British English “cot.”
Case Forms Pronunciation:
čeho /ˈtʃɛɦɔ/ - The “č” is a postalveolar affricate like English “ch” in “church.” The “h” is voiced, like English “h” but maintained between vowels.
čemu /ˈtʃɛmu/ - Same initial sound, with the dative ending “-emu.”
čem /tʃɛm/ - Shorter form for locative, always used with prepositions.
čím /tʃiːm/ - Note the long vowel “í” /iː/, marked by the háček-like acute accent.
Spelling Conventions:
The grapheme “č” (c with háček/caron) represents /tʃ/. This diacritical mark is essential - never omit it, as “c” and “č” represent completely different sounds.
Stress Pattern:
Czech stress always falls on the first syllable. In all forms of “co,” the stress is initial: CO, ČEho, ČEmu, ČÍm. Prepositions take the stress from the following word, so “o čem” is pronounced /ˈɔtʃɛm/ with stress on “o.”
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This lesson is part of the Latinum Institute Czech Language Course, which follows a systematic frequency-based approach to vocabulary acquisition. By learning the most common words in Czech, students rapidly build practical communication skills.
The Latinum Institute has been creating online language learning materials since 2006, specializing in the construed reading method that accelerates comprehension through interlinear glossing.
The course progresses through the 1000 most frequent words in Czech, ensuring that students master the vocabulary that accounts for approximately 80% of everyday communication.
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