Ovo je upozorenje.

Ovo means this.

In this sentence, ovo is the neuter singular form of the demonstrative this. Croatian demonstratives change form depending on the gender of the noun they refer to.

Here it matches upozorenje, which is a neuter noun.

Related forms:

• ovaj = this (masculine)
• ova = this (feminine)
• ovo = this (neuter)

So Ovo je upozorenje is literally This is a warning.

Because upozorenje is a neuter noun.

In Croatian, words like this must agree with the noun’s grammatical gender:

• masculine: ovaj
• feminine: ova
• neuter: ovo

Since upozorenje ends in -je, it is neuter, so ovo is the correct form.

Je means is.

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

So:

• ovo = this
• je = is
• upozorenje = warning

Together: This is a warning.

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

So upozorenje can mean:

• a warning
• the warning

The exact meaning depends on context.

That is very normal in Croatian. English learners often expect a separate word for a, but there isn’t one.

It is in the nominative singular.

In a sentence like Ovo je upozorenje, both parts are in the nominative because this is an equational sentence: one thing is being identified as another.

So:

• ovo = nominative
• upozorenje = nominative singular

This is similar to saying:

• To je kuća = That is a house
• Ovo je pitanje = This is a question

Upozorenje is neuter.

A good clue is the ending -e in the nominative singular, especially with nouns ending in -nje or -je, which are often neuter.

So:

• upozorenje = warning
• gender: neuter

Because it is neuter, you use:

• ovo upozorenje = this warning

A helpful approximate pronunciation is:

u-po-zo-REN-ye

A few notes:

• u sounds like oo in food
• o is a clear short o, not a diphthong
• r is rolled or tapped
• nj is like the ny sound in canyon
• je at the end sounds roughly like ye

So the end -nje is not pronounced like English nj; it is a soft nye sound.

Yes, Croatian word order is more flexible than English, but Ovo je upozorenje is the most neutral and natural order.

You may also see:

• To je upozorenje = That is a warning / It is a warning

In some contexts, word order can shift for emphasis, but for a learner, Ovo je upozorenje is the standard pattern to remember.

Both can sometimes translate as this/that/it, depending on context, but they are not identical.

• ovo usually means this — something near the speaker or being directly presented
• to often means that, or sometimes it/that thing

So:

• Ovo je upozorenje = This is a warning
• To je upozorenje = That is a warning or It is a warning

In real speech, to je is extremely common when identifying something.

To make it negative, use nije:

• Ovo nije upozorenje. = This is not a warning.

To make it a yes/no question, Croatian often uses intonation in speech:

• Ovo je upozorenje? = Is this a warning?

A more formal or explicit question uses je li:

• Je li ovo upozorenje? = Is this a warning?

So the basic pattern is:

• statement: Ovo je upozorenje.
• negative: Ovo nije upozorenje.
• question: Je li ovo upozorenje?

Yes. Upozorenje is related to the verb upozoriti, which means to warn.

So:

• upozoriti = to warn
• upozorenje = warning

This can help you build vocabulary:

• upozoriti nekoga = to warn someone
• dati upozorenje = to give a warning

Recognizing these word families is very useful in Croatian.

Yes, absolutely. Ovo je upozorenje is natural Croatian.

You might hear it:

• when showing a sign
• when pointing to a notice on a screen
• when introducing an official statement
• when emphasizing that something should be taken seriously

Depending on context, a speaker might also say:

• To je upozorenje.
• Ovo je samo upozorenje. = This is only a warning.
• Ovo nije šala, ovo je upozorenje. = This is not a joke, this is a warning.

So the sentence is short, simple, and completely idiomatic.