Vatra je opasna.

Because opasna has to agree with vatra in gender, number, and case.

• vatra = a feminine singular noun
• so the adjective must also be feminine singular
• the adjective opasan changes like this in the singular:
  • opasan = masculine
  • opasna = feminine
  • opasno = neuter

So Vatra je opasna is correct because vatra is feminine.

Je is the 3rd person singular present tense of the verb biti = to be.

So:

• vatra = fire
• je = is
• opasna = dangerous

It works just like is in English.

In Croatian, every noun has a grammatical gender: masculine, feminine, or neuter.

Vatra is a feminine noun. One clue is that many feminine nouns end in -a, and vatra does too. That is why the adjective must also take the feminine form opasna.

Keep in mind that grammatical gender does not always mean biological gender. A thing like fire can still be grammatically feminine.

Yes. Adjectives are usually listed in dictionaries under the masculine singular form, so you will usually find:

• opasan = dangerous

But in actual sentences, the adjective changes to match the noun:

• opasan pas = a dangerous dog
• opasna vatra = dangerous fire
• opasno more = a dangerous sea

So opasna is just the correct matching form here.

Croatian does not have articles like English a/an and the.

So Vatra je opasna can mean:

• Fire is dangerous
• The fire is dangerous

The exact meaning depends on the context. Croatian usually lets context do the job that articles do in English.

Yes, Croatian word order is more flexible than English word order.

The neutral, standard order here is:

• Vatra je opasna.

But you could also hear:

• Opasna je vatra.

That version puts more focus or emphasis on opasna or sounds more stylistically marked. English word order is much stricter, but Croatian can move elements around more easily.

Vatra is in the nominative singular because it is the subject of the sentence.

The adjective opasna is also in the nominative singular because it is describing the subject through the verb biti.

So this is a basic subject + to be + adjective sentence:

• vatra = nominative singular
• je
• opasna = nominative singular feminine

You make it negative by changing je to nije:

• Vatra nije opasna. = Fire is not dangerous.

So:

• je = is
• nije = is not

This is a very common pattern in Croatian.

A simple approximate pronunciation is:

VAH-tra yeh oh-PAHS-nah

A few useful points:

• v sounds like English v
• r in Croatian is trilled or tapped more than in English
• j is pronounced like English y in yes
• a is usually like a in father
• Croatian spelling is quite phonetic, so words are usually pronounced much as they are written

It can mean either, depending on context.

In a general statement:

• Vatra je opasna. = Fire is dangerous.

In a specific situation, it could also mean:

• The fire is dangerous.

Because Croatian has no articles, context tells you whether the meaning is general or specific.

In a normal standard sentence like this, no. You should keep je:

• Vatra je opasna.

Leaving it out would sound incomplete in standard Croatian:

• Vatra opasna. ❌

You may sometimes see omissions in headlines, notes, poetry, or very informal speech, but for learners, it is best to include je in full sentences.