Javi mi ako ne budeš mogao doći na sastanak.

Javi is the imperative of javiti, so it means let me know, tell me, or inform me.

So javi mi literally means let to me be known / notify me, but in natural English it is simply let me know.

It is in the imperative because the speaker is giving an instruction or request:

• Javi mi... = Let me know...

This is very common in Croatian.

Mi is the dative clitic form of ja (I / me), and here it means to me.

So:

• javi mi = let me know
• literally: inform to me

Croatian often uses the dative for the person receiving information, help, gifts, etc.

Compare:

• Daj mi knjigu. = Give me the book.
• Reci mi. = Tell me.
• Javi mi. = Let me know.

Ako means if.

This sentence sets up a condition:

• ako ne budeš mogao doći na sastanak = if you will not be able to come to the meeting

So ako is exactly the word you would expect here.

This is one of the most common questions learners have.

Ne budeš mogao is a future-oriented form, used because the sentence refers to a possible situation in the future:

• Javi mi ako ne budeš mogao doći... = Let me know if you won’t be able to come...

By contrast:

• ako ne možeš doći often sounds more present/general: if you can’t come
• ako ne budeš mogao doći points more clearly to a future occasion

In everyday speech, people may use either form depending on style and context, but ne budeš mogao is very natural when talking about a future event such as a meeting.

It is a combination used to express future ability.

Breakdown:

• budeš = 2nd person singular form of biti used in the so-called future II
• mogao = past active participle of moći

Together:

• budeš mogao = you will be able
• ne budeš mogao = you will not be able

This kind of structure appears especially after words like ako (if) and kad/kada (when) when referring to the future.

Because after budeš Croatian uses the l-participle form of the verb, not the infinitive.

So:

• infinitive: moći = to be able
• participle: mogao = masculine singular
• mogla = feminine singular
• mogli = masculine plural / mixed plural
• mogle = feminine plural

Since the sentence is addressed to an implied ti and the form shown is masculine singular, it is:

• budeš mogao

If the speaker were talking to a woman, it would be:

• Javi mi ako ne budeš mogla doći na sastanak.

Yes.

In forms like this, the participle agrees with the subject in gender and number.

So:

• to a man: ako ne budeš mogao
• to a woman: ako ne budeš mogla
• to several people: ako ne budete mogli

This is something English does not do, so it often stands out to learners.

Because moći is followed by another verb in the infinitive.

So:

• moći doći = to be able to come
• ne budeš mogao doći = you will not be able to come

This is the normal pattern:

• Mogu pomoći. = I can help.
• Ne mogu spavati. = I can’t sleep.
• Hoćeš li moći doći? = Will you be able to come?

Doći means to come / arrive, and na sastanak means to the meeting.

With na, Croatian uses:

• accusative when there is movement toward something
• locative when there is location at/on something

Here there is movement to the meeting:

• doći na sastanak = come to the meeting

Compare:

• Idem na sastanak. = I’m going to the meeting.
• Na sastanku sam. = I’m at the meeting.

So:

• na sastanak = accusative
• na sastanku = locative

Because after na with motion, the noun goes into the accusative singular.

The noun is:

• nominative: sastanak = meeting
• accusative singular: sastanak

For this masculine inanimate noun, nominative and accusative have the same form, which is why you do not see a change.

So even though the form looks unchanged, it is still accusative because the grammar requires it.

It is informal singular, because it uses the ti forms:

• javi
• budeš

You would say this to one person you address as ti.

The formal or plural version would be:

• Javite mi ako ne budete mogli doći na sastanak.

That can mean either:

• speaking politely to one person (Vi), or
• speaking to more than one person

Yes. Croatian word order is fairly flexible.

You could also say:

• Ako ne budeš mogao doći na sastanak, javi mi.

This means the same thing:

• If you won’t be able to come to the meeting, let me know.

The original version starts with the main request:

• Javi mi... This can sound a bit more direct and natural in everyday speech.

Yes, it would be possible, and in everyday conversation it is very common.

Compare:

• Javi mi ako ne možeš doći na sastanak.
• Javi mi ako ne budeš mogao doći na sastanak.

The first is simpler and more conversational. The second is a bit more explicitly future-oriented.

In many real-life situations, both are acceptable, but ne budeš mogao fits especially well when the inability would happen at some later point.

Not exactly, though they overlap.

• reći = to say / tell
• javiti = to let know / notify / inform

In this sentence, javiti is more natural because the idea is inform me if something changes.

You could say:

• Reci mi ako ne budeš mogao doći.

That is understandable, but javi mi sounds more idiomatic for let me know.