Oni znaju da je pušenje štetno.

They know that smoking is harmful.

Breakdown of Oni znaju da je pušenje štetno.

• biti: to be
• oni: they
• znati: to know
• da: that
• štetan: harmful
• pušenje: smoking

Questions & Answers about Oni znaju da je pušenje štetno.

What does each word in Oni znaju da je pušenje štetno correspond to, and what is the basic structure?

• oni – they (3rd person plural pronoun, nominative)
• znaju – know (3rd person plural present of znati)
• da – that (conjunction introducing a subordinate clause)
• je – is (3rd person singular of biti, the verb to be)
• pušenje – smoking (a verbal noun, literally “the act of smoking”)
• štetno – harmful (adjective, neuter singular form)

Structure:

• Main clause: Oni znaju – They know
• Subordinate da-clause (what they know): da je pušenje štetno – that smoking is harmful

So the whole sentence is: They know that smoking is harmful.

Why is pušenje used instead of the infinitive pušiti for “smoking”?

English often uses a gerund (-ing form) as a subject: Smoking is harmful.

Croatian typically uses a verbal noun for this function:

• verb: pušiti – to smoke
• verbal noun: pušenje – smoking, the act of smoking

In this sentence, pušenje is a noun in the nominative acting as the subject of je štetno.

You can use the infinitive pušiti in some constructions, but usually after the predicate adjective/verb, for example:

• Štetno je pušiti. – It is harmful to smoke.
  (literally: Harmful is to smoke.)

But if you want “Smoking is harmful” with “smoking” as the subject, the natural form is Pušenje je štetno (or inside the da-clause: da je pušenje štetno).

Why does štetno end in -o and not in -an or -a?

Croatian adjectives agree with the noun in gender, number, and case.

• The base adjective is štetan – harmful
  
  • masculine: štetan
  • feminine: štetna
  • neuter: štetno

The noun pušenje is neuter singular (like many nouns ending in -nje), so the adjective must also be neuter singular:

• pušenje (neuter) → štetno (neuter form of the adjective)

So:

• pušenje je štetno – smoking is harmful
• alkohol je štetan – alcohol is harmful (masculine)
• cigara je štetna – the cigarette is harmful (feminine)

Why is the order da je pušenje štetno and not da pušenje je štetno, which looks closer to English “that smoking is harmful”?

The key point is the little verb je. It’s a clitic (an unstressed short form) of biti (to be). In Croatian, clitics must appear very early in the clause, usually in the second position (after the first stressed word or phrase).

In the da-clause:

• da – conjunction (often counts as the first position)
• je – clitic verb (must come immediately after da)
• pušenje štetno – the rest of the clause

So the standard order is:

• da je pušenje štetno

The version ✗ da pušenje je štetno is ungrammatical in standard Croatian because je is too late in the clause. English word order rules don’t apply here; Croatian is strongly shaped by the clitic-position rule.

Are there other correct word orders for the part je pušenje štetno?

Yes, you have some flexibility, but je must stay very early.

Common, natural options inside the da-clause:

• da je pušenje štetno – neutral, most common
• da je štetno pušenje – emphasizes štetno (harmful) a bit more; often used in certain styles or contexts

Less common but still grammatical with different emphasis:

• da pušenje jest štetno – using jest (a stressed form of je) allows pušenje to come first and adds emphasis to the verb, something like: that smoking really is harmful. Here jest is not a clitic, so it can move.

But:

• ✗ da pušenje je štetno – sounds wrong in standard Croatian, because je as a clitic is too late.

So you can play with order somewhat, but you must respect clitic placement and accept that word order often carries subtle emphasis changes.

What exactly does da do here, and can it be omitted like English sometimes omits “that”?

Here da is a conjunction introducing a content clause (a “that-clause”) which functions as the object of znaju:

• Oni znaju [da je pušenje štetno].
  → They know [that smoking is harmful].

In English, you can often drop that:
They know smoking is harmful.

In Croatian, in this type of sentence, you normally cannot omit da. Saying:

• ✗ Oni znaju je pušenje štetno.

is incorrect. With verbs like znati, misliti, reći, čuti, etc., the content clause almost always needs da in standard speech:

• Mislim da je to istina. – I think (that) it is true.
• Rekli su da dolaze. – They said (that) they are coming.

So here da is obligatory.

Do I have to say oni, or can I just say Znaju da je pušenje štetno?

You can absolutely drop oni:

• Oni znaju da je pušenje štetno.
• Znaju da je pušenje štetno.

Both are correct and mean the same thing.

Croatian is a pro-drop language: the verb ending (-aju in znaju) already tells you person and number (3rd person plural – they), so the subject pronoun oni is often omitted unless:

• you want to emphasize they (as opposed to someone else), or
• the subject might otherwise be unclear from context.

In normal conversation, Znaju da je pušenje štetno is perfectly natural.

How would I make this sentence negative: “They don’t know that smoking is harmful”?

You negate the main verb znati with ne:

• Oni ne znaju da je pušenje štetno.
• (without pronoun) Ne znaju da je pušenje štetno.

Points to note:

• ne comes directly before the verb it negates: ne znaju.

• The da-clause and its internal verb je stay unchanged, because you’re negating knowing, not the fact:

  • They don’t know [that smoking is harmful].

If you wanted to negate the statement about smoking instead, you’d say:

• Oni znaju da pušenje nije štetno. – They know that smoking is not harmful.

How do I turn this into a yes–no question: “Do they know that smoking is harmful?”

There are two common ways.

1. Using li (more neutral / standard formal):

   • Znaju li da je pušenje štetno? – Do they know that smoking is harmful?

   Here:

   • You move the verb znaju to the beginning.
   • Add the clitic li right after the verb to mark a yes–no question.

2. Using da li (very common in speech, slightly less formal in some styles):

   • Da li znaju da je pušenje štetno?

Both are widely understood. In writing, especially more formal, Znaju li…? is often preferred. The da je pušenje štetno part stays unchanged.

How do I change the tense inside the da-clause, like in “They know that smoking was harmful” or “will be harmful”?

You keep znaju in the present (they know now), and change the verb je plus sometimes the adjective:

1. “They know that smoking was harmful.”

   • Oni znaju da je pušenje bilo štetno.
     Literally: They know that smoking was harmful.

   Here:

   • bilo – past participle (neuter) of biti (to be).
   • pušenje is still the subject; bilo štetno = was harmful.

2. “They know that smoking will be harmful.”

   • Oni znaju da će pušenje biti štetno.
     Literally: They know that smoking will be harmful.

   Here:

   • će – future tense auxiliary (clitic).
   • biti – infinitive of to be.
   • će must come very early in the clause (clitic position), just like je does.

You could also shift znaju to other tenses if you want:

• Znali su da je pušenje štetno. – They knew that smoking is/was harmful.
• Znat će da je pušenje štetno. – They will know that smoking is harmful.