Ovaj ključ je dar.

Because ovaj must agree with the noun it describes in gender, number, and case.

Here, ključ is:

• masculine
• singular
• nominative

So the correct form is ovaj.

Compare:

• ovaj = this, masculine singular
• ova = this, feminine singular
• ovo = this, neuter singular

In Croatian, grammatical gender is not the same as biological sex. An object can be grammatically masculine, feminine, or neuter without implying anything about being male or female.

Ključ is simply a masculine noun. One clue is that many Croatian nouns ending in a consonant are masculine.

So ključ is masculine because of grammar, not meaning.

All the main nouns here are in the nominative.

• ovaj ključ is nominative because it is the subject of the sentence.
• dar is also nominative because it is a predicate noun after je.

So:

• ovaj = masculine singular nominative
• ključ = masculine singular nominative
• dar = masculine singular nominative

After the verb biti (to be), Croatian normally uses the nominative for a predicate noun.

So:

• Ovaj ključ je dar. = correct
• darom would not be the normal form here

This is similar to sentences like:

• On je učitelj. = He is a teacher.
• Ovo je problem. = This is a problem.

So dar stays in its basic dictionary form.

Je means is. It is the 3rd person singular present form of biti (to be).

So the structure is:

• Ovaj ključ = this key
• je = is
• dar = a gift / gift

A useful extra point: je is a clitic, which means it is unstressed and tends to appear near the beginning of the sentence, often after the first whole phrase.

Croatian does not have articles like English a, an, or the.

So dar can mean:

• a gift
• sometimes the gift, depending on context

In this sentence, English would usually translate it as a gift:

• Ovaj ključ je dar. = This key is a gift.

Croatian relies on context, word order, and words like ovaj (this) instead of articles.

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

Ovaj ključ je dar. is a normal, neutral way to say it.

Other orders are possible, but they usually change the emphasis. For example, putting dar earlier can emphasize that it is a gift.

However, not every rearrangement sounds equally natural, and je has its own placement rules because it is a clitic. So for a learner, Ovaj ključ je dar. is a very safe and natural model.

A rough English-friendly guide is klyooch.

The tricky parts are:

• lj: a soft sound somewhat like the lli in million for many English speakers
• č: like ch in church

So:

• ključ ≈ klyooch

And the whole sentence is roughly:

• OH-vai klyooch yeh dar

That is only an approximation, but it is a good start.

Both dar and poklon can mean gift.

A learner should know this difference:

• poklon is very common in everyday speech
• dar is also correct, but it can sound a bit more formal, literary, or expressive depending on context

So Ovaj ključ je dar. is perfectly good Croatian, but in casual conversation you may also hear:

• Ovaj ključ je poklon.

You would say:

Ovaj ključ nije dar.

Here, nije means is not.

So:

• je = is
• nije = is not

That is the standard negation of this sentence.