Ugovorna obveza traje tri godine.

Because ugovorna is an adjective, and in Croatian adjectives must agree with the noun they describe in gender, number, and case.

Here it describes obveza, which is:

• feminine
• singular
• nominative

So the adjective also has the feminine singular nominative form: ugovorna.

It means contractual or based on a contract.

It comes from the noun ugovor, meaning contract. So:

• ugovor = contract
• ugovorna obveza = contractual obligation

It does not usually mean agreed in this context. The idea is that the obligation exists under a contract.

Obveza means obligation, duty, or commitment.

In legal or business language, it often means an obligation that someone has to fulfill. In this sentence, it has a fairly formal/legal feel, so obligation is the best match.

Also, obveza is a feminine noun, which is why the adjective is ugovorna.

Traje is the present-tense form of trajati, which means to last or to continue for a period of time.

So traje means lasts.

It is 3rd person singular, because the subject is singular:

• ugovorna obveza = one contractual obligation
• therefore: traje

It is in the nominative case, because it is the subject of the sentence.

You can ask yourself: What lasts three years? Answer: ugovorna obveza

That makes it the subject, so nominative is used.

Because Croatian does not have articles.

So Croatian usually does not have separate words for:

• a / an
• the

Whether the meaning is definite or indefinite is understood from context.

So ugovorna obveza can mean:

• a contractual obligation
• the contractual obligation

depending on the situation.

Because Croatian often expresses duration with the noun phrase directly, without a preposition.

After verbs like trajati, Croatian uses a time expression meaning for three years simply as:

• tri godine

So:

• traje tri godine = lasts for three years

You do not need a separate word for for here.

Because Croatian number phrases change form depending on the number.

With 2, 3, 4, you normally get:

• dvije godine
• tri godine
• četiri godine

But with 5 and higher, you get:

• pet godina
• šest godina
• deset godina

So tri godine is the correct pattern.

A useful mini-pattern to memorize is:

• jedna godina
• dvije / tri / četiri godine
• pet+ godina

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

The sentence as given, Ugovorna obveza traje tri godine, is the most neutral and natural order.

But you could also say:

• Tri godine traje ugovorna obveza.

That version puts more emphasis on the duration.

So word order can change for focus or style, but the original version is the safest neutral choice for learners.