In Croatian a preposition does not just sit in front of a noun — it governs it, forcing a specific case onto whatever follows. English prepositions do none of this: the noun looks the same after in, with, or without. So the English speaker's reflex is to pick the preposition and stop, leaving the noun in whatever case feels handy. The result is a steady stream of case errors. Worse, some prepositions take different cases depending on meaning — u + accusative for going in, u + locative for being in. This page catalogues the worst offenders as wrong→right pairs, each with the governing rule. The wider system is on the prepositions overview.
Motion takes the accusative; rest takes the locative
This is the big one, and it has no English analogue at all. With u (in/to) and na (on/to), the case flips with the meaning. Movement toward a goal takes the accusative; being at rest in a place takes the locative. Ask yourself "where to?" versus "where at?" — the answer chooses the case.
❌ Idem u gradu.
Wrong — 'idem' is motion toward, so 'u' needs the accusative 'grad', not the locative 'gradu'.
✅ Idem u grad.
I'm going into town. — motion toward a goal, so 'u' + accusative 'grad'.
❌ Živim u grad.
Wrong — 'živim' is a static state, so 'u' needs the locative 'gradu', not the accusative.
✅ Živim u gradu.
I live in town. — rest in a place, so 'u' + locative 'gradu'.
The same flip applies to na: stavi na stol (put it onto the table — accusative stol) versus na stolu je (it's on the table — locative stolu).
❌ Knjiga je na stol.
Wrong — a static location needs 'na' + locative 'stolu'.
✅ Knjiga je na stolu.
The book is on the table. — rest, so 'na' + locative 'stolu'.
The instrument of means is a bare instrumental — no 's'
English uses with for tools: write with a pen, cut with a knife. Croatian uses the bare instrumental with no preposition — the case itself carries "with/by means of." Adding s/sa turns the tool into a companion, which is either wrong or absurd.
❌ S olovkom pišem.
Wrong for 'with a pen' — 's olovkom' means 'accompanied by a pencil'; the instrument is the bare instrumental 'olovkom'.
✅ Pišem olovkom.
I write with a pen. — instrument of means = bare instrumental, no 's'.
❌ Idem na more s autom.
Wrong for 'by car' — 's autom' means 'together with a car'; the means is the bare instrumental 'autom'.
✅ Idem na more autom.
I'm going to the seaside by car. — means of transport = bare instrumental, no 's'.
Company DOES take 's' — and the instrumental
The flip side: when with really means in the company of someone, you must use s/sa plus the instrumental. Here the English speaker who learned "drop the preposition for the instrumental" overcorrects and drops it where it is required.
❌ Idem prijateljem.
Wrong — company needs the preposition; say 's prijateljem'.
✅ Idem s prijateljem.
I'm going with a friend. — accompaniment = 's/sa' + instrumental.
❌ Razgovaram šeficom.
Wrong — 'with the boss' is company, so add 's': 'sa šeficom'.
✅ Razgovaram sa šeficom.
I'm talking with the boss. — accompaniment + 's' (here 'sa' before the hissing 'š').
The rule of thumb: a tool or means is bare instrumental (olovkom, autom); a person you're with takes s/sa + instrumental (s prijateljem). The form sa (rather than s) appears before words starting with s, š, z, ž and certain clusters, purely for pronounceability.
bez always takes the genitive
Bez (without) is one of a whole family of prepositions that govern the genitive: bez, do, od, iz, kod, blizu, oko. The English speaker leaves the noun in the nominative because without never changes a noun in English.
❌ Kava bez šećer.
Wrong — 'bez' governs the genitive; say 'bez šećera'.
✅ Kava bez šećera.
Coffee without sugar. — 'bez' + genitive 'šećera'.
❌ Ne mogu bez kruh.
Wrong — 'bez' + genitive, so 'kruha'.
✅ Ne mogu bez kruha.
I can't go without bread. — 'bez' + genitive 'kruha'.
The same genitive reflex extends past prepositions to quantity words — puno (a lot of), malo (a little), čaša (a glass of) all govern the genitive too, which trips up the same learners for the same reason.
❌ Čaša voda, molim.
Wrong — 'a glass OF water' is the genitive: 'Čašu vode, molim'.
✅ Čašu vode, molim.
A glass of water, please. — 'čaša' takes the genitive 'vode' (and is itself accusative 'čašu' as the object of 'molim').
misliti na, not misliti o, for "think about"
A preposition trap that hides inside a verb. To express having someone on your mind, Croatian uses misliti na + accusative, not the o (about) you would predict from English. The construction misliti o exists, but means to hold an opinion about something — a different sense.
❌ Mislim o tebi cijeli dan.
Misleading — 'misliti o' means 'to have an opinion about'; for 'thinking of you' use 'misliti na'.
✅ Mislim na tebe cijeli dan.
I think about you all day. — 'misliti na' + accusative 'tebe' for having someone on your mind.
❌ Moraš misliti o budućnost.
Wrong twice — it should be 'na' for planning ahead, and the case must be accusative 'budućnost'.
✅ Moraš misliti na budućnost.
You have to think about the future. — 'misliti na' + accusative 'budućnost'.
Key Takeaways
- Motion vs rest flips the case after u and na: motion toward a goal → accusative (idem u grad), rest in a place → locative (živim u gradu). The verb decides.
- The instrument of means is a bare instrumental with no preposition (pišem olovkom, idem autom); adding s would mean "accompanied by."
- Company requires s/sa + instrumental (idem s prijateljem) — don't overcorrect and drop the preposition where it's needed.
- bez and its genitive-governing family (do, od, iz, kod) take the genitive (bez šećera, bez kruha).
- "Think about (someone)" is misliti na + accusative (mislim na tebe), not misliti o.
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Start learning Croatian→Related Topics
- Prepositions and Their CasesA2 — Every Croatian preposition governs a case — grouped by genitive, dative, accusative, locative, instrumental, plus the seven two-case prepositions.
- Preposition Pitfalls for English SpeakersB1 — The English-to-Croatian preposition mismatches that trip learners up — bare-case verbs like čekati, slušati, tražiti, plus misliti na, ovisiti o, and 'by car'.
- Accusative for Motion and DirectionA2 — Prepositions of destination that take the accusative.
- Locative for Static LocationA2 — Where something IS — the rest/position sense of u and na.
- Mistake: Subtle Preposition and Case MismatchesB2 — The preposition errors that persist past A2 — radi vs zbog, the location locative after na, kod plus genitive, the bare instrumental of transport, and days in the accusative.