Jedini uvjet je da dođeš na vrijeme.

Jedini means the only, while jedan means one / a.

So:

• jedan uvjet = one condition
• jedini uvjet = the only condition

In this sentence, the speaker is saying there is just one requirement, so jedini is the natural choice.

Because jedini is an adjective and it has to agree with the noun uvjet.

• uvjet is masculine singular
• so the adjective also takes the masculine singular form: jedini

Compare:

• jedini uvjet = the only condition
• jedina prilika = the only opportunity
• jedino rješenje = the only solution

So the ending changes depending on the gender of the noun.

Uvjet means condition, requirement, or stipulation, depending on context.

In this sentence, Jedini uvjet je... is something like:

• The only condition is...
• The only requirement is...

You may also encounter uslov, which can mean the same thing. Uvjet is the standard Croatian form, while uslov is more common in some other varieties of the language.

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

So:

• Jedini uvjet = the only condition
• je = is
• da dođeš na vrijeme = that you arrive / come on time

Literally, the structure is:

The only condition is that...

This is very similar to English.

Here da introduces a subordinate clause, similar to English that.

So:

• Jedini uvjet je da... = The only condition is that...

In Croatian, da is very common after expressions like:

• važno je da... = it is important that...
• želim da... = I want that...
• uvjet je da... = the condition is that...

So in this sentence, da links the main clause to the action that is required.

Croatian often uses da + present tense where English might use an infinitive or a that-clause.

Here, da dođeš means something like:

• that you come
• for you to come
• that you arrive

Using just doći after uvjet je would not sound natural here.

So:

• Jedini uvjet je da dođeš na vrijeme. = natural
• Jedini uvjet je doći na vrijeme. = not the normal way to say this meaning

Dođeš is the 2nd person singular present tense form of doći = to come / to arrive.

It means you come or, in this kind of sentence, you arrive.

The verb forms are:

• ja dođem = I come / arrive
• ti dođeš = you come / arrive
• on/ona/ono dođe = he/she/it comes / arrives

In this sentence, the speaker is addressing one person informally, so dođeš = you singular informal.

If speaking formally or to more than one person, it would be:

• Jedini uvjet je da dođete na vrijeme.

This is a very important Croatian pattern.

Doći is a perfective verb. Perfective present forms often do not describe a regular present action. Instead, especially after da, they often refer to a future or expected completed action.

So da dođeš na vrijeme means:

• that you arrive on time
• that you come on time

It is not describing what you are doing right now. It is describing what must happen.

This is normal in Croatian grammar.

Because na vrijeme usually goes naturally with verbs of arriving, coming, finishing, starting, etc.

• doći na vrijeme = to arrive on time
• stići na vrijeme = to get there on time
• biti na vrijeme is not the usual expression here

So dođeš na vrijeme is the idiomatic way to say you arrive on time.

A close alternative would be:

• Jedini uvjet je da stigneš na vrijeme.

That also means The only condition is that you get there on time.

Na vrijeme means on time, in time, or punctually, depending on context.

In this sentence, the best translation is on time.

This is a fixed expression:

• doći na vrijeme = come/arrive on time
• stići na vrijeme = arrive in time / on time
• budi na vrijeme = be on time

It does not literally mean something like on the time in a word-for-word English sense. It is just the standard Croatian phrase.

Because Croatian usually leaves out subject pronouns when they are already clear from the verb ending.

• dođeš already tells us the subject is you singular informal

So:

• da dođeš na vrijeme = natural
• da ti dođeš na vrijeme = possible, but more emphatic

Including ti would usually add contrast or emphasis, like:

• Jedini uvjet je da ti dođeš na vrijeme, a ne netko drugi. = The only condition is that you arrive on time, not someone else.

Yes, Croatian word order is fairly flexible, although some versions sound more neutral than others.

The most neutral version is:

• Jedini uvjet je da dođeš na vrijeme.

You could also hear:

• Uvjet je samo da dođeš na vrijeme.
• Samo je uvjet da dođeš na vrijeme.

These are slightly different in emphasis, but the basic meaning stays close.

The given sentence is very natural and clear.

It is grammatically informal because of dođeš, which is the ti form.

So this is used when speaking to:

• one person
• in an informal setting

For formal singular or plural, Croatian uses vi, so the sentence becomes:

• Jedini uvjet je da dođete na vrijeme.

That can mean either:

• The only condition is that you arrive on time. (formal singular)
• The only condition is that you all arrive on time. (plural)

So the form of the verb tells you the level of formality.