Learn Hardcore Croatian: Pušenje je štetno za pluća, tako da grad želi zabraniti cigarete u kafićima. - Smoking is harmful for the lungs, so the city wants to ban cigarettes in cafés.

As a subject, the verbal noun (pušenje) is more common and sounds more neutral/standard.
The infinitive as subject (Pušiti je štetno) is also understandable, but can sound a bit more informal or stylistically marked.

So Pušenje je štetno… is the most natural neutral formulation.

What is štetno grammatically, and why is it in that form?

Štetno is the neuter singular form of the adjective štetan (harmful).

It appears here in the predicative position (after je) and agrees in gender and number with the subject pušenje:

pušenje – neuter singular noun
štetno – neuter singular adjective form

Compare:

Pušenje je štetno. – Smoking is harmful.
Cigarete su štetne. – Cigarettes are harmful. (cigarete = feminine plural → štetne)

Why is it štetno za pluća instead of something like štetno plućima?

The preposition za with the accusative is a very common way to express harmful to X:

štetno za pluća = harmful to the lungs
štetno za zdravlje = harmful to health
štetno za djecu = harmful to children

Here pluća is in the accusative plural, because za always takes the accusative when it means “for / to (the detriment of)”.

You can say štetno plućima (using the dative plural plućima), and it will also be understood, but:

za + accusative is more straightforward and much more common in this “harmful to X” structure.
štetno za pluća is the idiomatic default.

What case is pluća, and is it always plural?

Pluća means lungs, and it is:

Nominative plural when it’s the subject:
- Pluća su važna za disanje. – Lungs are important for breathing.
Accusative plural when it follows za:
- štetno za pluća

This noun is plural-only (pluralia tantum) in normal usage, just like lungs in English. You don’t normally use a singular form for a single lung in everyday speech; you still say pluće in medical/technical contexts, but learners can safely treat pluća as “always plural” in typical sentences.

What exactly does tako da mean here, and is it the same as so or so that in English?

In this sentence, tako da introduces a result/consequence:

Pušenje je štetno za pluća, tako da grad želi zabraniti cigarete…
Smoking is harmful to the lungs, so the city wants to ban cigarettes…

Here tako da ≈ so / therefore / as a result.

Notes:

tako da can sometimes mean in such a way that, describing manner:
- Organizirao je posao tako da svi budu zadovoljni.
  – He organised the work in such a way that everyone is satisfied.
In your sentence it’s clearly result, not manner.

You could also say:

…zato grad želi… or
…zbog toga grad želi…

but tako da is very natural in spoken and written Croatian.

Could the word order be changed, for example to Grad želi zabraniti cigarete u kafićima, jer je pušenje štetno za pluća?

Yes, that’s perfectly possible and natural; it just changes the structure a bit:

Original:
Pušenje je štetno za pluća, tako da grad želi zabraniti cigarete u kafićima.
→ First states the fact (smoking is harmful), then gives the result (so the city wants to ban…).
Alternative:
Grad želi zabraniti cigarete u kafićima, jer je pušenje štetno za pluća.
→ Starts with the decision (the city wants to ban), then gives the reason (jer = because).

Both are grammatical. Choice depends on which part you want to emphasize first: the harmfulness of smoking or the city’s decision.

Why is želi zabraniti used, and how does this construction work?

Želi zabraniti is verb + infinitive:

želi – 3rd person singular of željeti (to want)
zabraniti – infinitive (to ban / to forbid)

So grad želi zabraniti = the city wants to ban.

This pattern is very common:

Želim učiti hrvatski. – I want to learn Croatian.
Ne želimo čekati. – We don’t want to wait.

You could also use hoće in some contexts, but:

željeti is more neutral and polite (want, would like)
htjeti/hoće can be a bit stronger, sometimes closer to will / is determined to depending on context.

Why zabraniti cigarete and not zabraniti pušenje? Are both correct?

Both are correct, but there’s a slight difference in focus:

zabraniti cigarete u kafićima
– to ban cigarettes in cafés (the objects themselves; for example, you can’t bring them in or sell them there)
zabraniti pušenje u kafićima
– to ban smoking in cafés (the activity; you might still be allowed to carry cigarettes in your pocket)

In real-world usage, zabraniti pušenje u kafićima is often more precise if the goal is to stop the act of smoking inside. The sentence you were given is fully grammatical and understandable; it just frames the ban in terms of the cigarettes themselves.

What case is cigarete, and why is it in that form?

Cigarete here is accusative plural, because it is the direct object of zabraniti:

(Grad) želi zabraniti cigarete. – (The city) wants to ban cigarettes.

For a regular feminine noun like cigara / cigareta:

Nominative plural: cigarete (subject) – Cigarete su skupe.
Accusative plural: cigarete (object) – Kupujem cigarete.

So nominative and accusative plural look the same; the role is understood from the sentence structure.

Why is it u kafićima and not u kafiće?

The preposition u can take either locative or accusative, depending on the meaning:

u + locative → location (where?)
- u kafićima – in cafés (location, static)
u + accusative → direction (into where?)
- u kafiće – into cafés (movement towards)

In the sentence:

zabraniti cigarete u kafićima = to ban cigarettes in cafés (location: where the ban applies), so the locative plural kafićima is correct.

What does kafić mean, and is it different from kavana or bar?

Kafić is a very common word in Croatian for a café / coffee bar / small bar where people drink coffee, soft drinks, sometimes alcohol, and socialize.

Rough differences:

kafić – the everyday, modern word; informal or neutral.
kavana – traditionally a more old-fashioned or somewhat more formal café (often larger, with pastries, a “Viennese café” feel).
bar – borrowed from English; often used for places that are more about alcohol/nightlife, but usage overlaps.

In your sentence, u kafićima simply means in cafés/bars in the general sense where people sit and drink.