Learn Hardcore Croatian: U vlaku čitam časopis o jezicima i tražim prijevod teških riječi. - On the train I read a magazine about languages and look for a translation of difficult words.

u vlaku literally means in the train.
The preposition u with the locative case (vlaku) is used for being inside enclosed vehicles and spaces:
- u vlaku – in the train
- u autobusu – in the bus
- u autu – in the car

na vlaku would literally mean on top of the train (e.g. standing on the roof), so it would sound wrong for normal “riding the train”.

Grammatically:

Dictionary form: vlak (train) – nominative singular
Locative singular: vlaku (after u for location)

What form is čitam, and why isn’t it čitati?

čitati is the infinitive: to read.

čitam is the present tense, 1st person singular of čitati:

čitam – I read / I am reading
čitaš – you (sg) read
čita – he/she/it reads

Croatian has only one present form for both English I read and I am reading. Context decides how you translate it, so čitam can be:

“I read a magazine on the train” (habit)
“I am reading a magazine on the train” (right now)

What’s the difference between časopis and novine?

Both are kinds of printed media, but they’re not the same:

časopis – magazine, journal
- usually periodic (weekly, monthly), often on a specific topic (languages, fashion, science, etc.)
novine – newspaper(s)
- daily/weekly news, plural-only noun in Croatian

Examples:

čitam časopis – I’m reading a magazine
čitam novine – I’m reading the newspaper

What case is jezicima in časopis o jezicima, and why is that ending used?

jezicima is locative plural of jezik (language, tongue).

jezik (language):

nominative sg: jezik
genitive sg: jezika
locative sg: jeziku
nominative pl: jezici
locative pl: jezicima

The preposition o (about) always takes the locative case:

o jeziku – about a language
o jezicima – about languages

So časopis o jezicima literally means a magazine about languages.

Does časopis o jezicima mean “magazine about languages” or “magazine of languages”? Is o always “about”?

Here it clearly means magazine about languages.

o
- locative is typically translated as about:
  - knjiga o povijesti – a book about history
  - film o ratu – a film about war
  - časopis o jezicima – a magazine about languages

“Magazine of languages” in the sense “for” or “belonging to” would usually be phrased differently, e.g.:

časopis za jezike – a magazine for languages (more like for learning languages)
jezični časopis – linguistic magazine / language magazine (adjective form)

What does tražim mean exactly? Is it “I search”, “I look for”, or “I ask for”? How is it different from pitam?

tražim is the present 1st person singular of tražiti, and it means I look for / I am looking for / I seek.

In this sentence:

tražim prijevod – I’m looking for a translation.

Typical meanings of tražiti:

tražiti ključeve – to look for keys
tražiti posao – to look for a job
tražiti pomoć – to ask for help / to seek help

pitati = to ask (a question):

pitam učitelja – I ask the teacher
pitam što to znači – I ask what that means

So:

tražim prijevod – I look for a translation (I’m trying to find it)
pitam za prijevod – I ask (someone) for a translation

Why is it prijevod teških riječi and not prijevod teške riječi or prijevod teške reči? What is going on with riječi?

Several things are happening here: number, case, and a slightly irregular noun.

riječ is the base noun
- riječ – word (singular)
- riječi – words (plural nominative)
In prijevod teških riječi we talk about more than one word:
- teških riječi = of difficult words (plural)
The phrase prijevod teških riječi uses the genitive plural:
- prijevod čega? – translation of what? → teških riječi
- So riječi here is genitive plural (same form as nominative plural for this noun).
Spelling: riječ / riječi (with č).
reči is Serbian spelling (ekavian); Croatian uses riječ / riječi.

So:

prijevod teške riječi – translation of a difficult word (one word, genitive singular)
prijevod teških riječi – translation of difficult words (several words, genitive plural)

Why is the adjective teških used and not teške in teških riječi?

Adjectives must agree with nouns in gender, number, and case.

Noun: riječi here is feminine plural, genitive case (genitive plural of riječ).
So the adjective težak (difficult, heavy) must also be feminine, plural, genitive → teških.

Forms of težak (just the plural nominative vs genitive for comparison):

Nominative plural feminine: teške riječi – difficult words (as subject/object in nominative)
Genitive plural feminine: teških riječi – of difficult words

Because prijevod governs genitive (prijevod čega?), we need teških riječi, not teške riječi.

Why is prijevod singular in tražim prijevod teških riječi? Could it be plural, like tražim prijevode?

Both are possible, but they mean slightly different things:

tražim prijevod teških riječi
- I’m looking for the/a translation of the difficult words (one translation that covers them).
tražim prijevode teških riječi
- I’m looking for translations of the difficult words (several translations, maybe different options or different words).

In your sentence, singular prijevod suggests you’re looking for a single coherent translation (e.g. of a phrase or sentence containing difficult words).

What aspect is used in čitam and tražim? How would the meaning change with forms like pročitam or potražim / pronađem?

čitam and tražim are imperfective (ongoing, repeated, or uncompleted actions).

čitam časopis – I am reading a magazine / I read a magazine
tražim prijevod – I am looking for a translation

Perfective counterparts emphasize completion:

pročitati – to read (to the end, finish reading)
- pročitam časopis – I (will) read the magazine / I’ll finish reading it.
potražiti – to look for (with focus on the attempt as a single action)
- potražit ću prijevod – I’ll (try to) look for a translation.
pronaći / naći – to find
- pronađem prijevod – I find a translation.

In your sentence, the imperfective makes sense because it describes what you’re currently doing on the train, not the finished result.

How flexible is the word order? Could I say Čitam u vlaku časopis o jezicima or U vlaku tražim prijevod teških riječi i čitam časopis o jezicima?

Croatian word order is relatively flexible, especially compared to English. Your alternatives are grammatically possible, but the focus/emphasis can shift slightly.

Original:

U vlaku čitam časopis o jezicima i tražim prijevod teških riječi.
→ Neutral: On the train, I read a magazine about languages and look for a translation of difficult words.

Possible variations:

Čitam u vlaku časopis o jezicima i tražim prijevod teških riječi.
Slightly more focus on čitam at the start; still natural.
U vlaku tražim prijevod teških riječi i čitam časopis o jezicima.
Puts tražim prijevod… first among the activities, as if that’s more important.

As long as:

the subject–verb–object relationships stay clear, and
clitics (short unstressed words like se, ga, ih) are in proper second position (not present here),

you have quite a bit of freedom.

Can you list all the cases used for the nouns in this sentence and say why each case is used?

Sentence: U vlaku čitam časopis o jezicima i tražim prijevod teških riječi.

Nouns and their cases:

vlaku – locative singular
- Preposition u (in) + locative for location: u vlaku – in the train.
časopis – accusative singular
- Direct object of čitam: I read what? → časopis.
jezicima – locative plural
- Preposition o (about) + locative: o jezicima – about languages.
prijevod – accusative singular
- Direct object of tražim: I look for what? → prijevod.
teških riječi – genitive plural
- prijevod čega? – translation of what? → teških riječi (of difficult words).
- Genitive plural because it depends on prijevod and indicates “of”.