Ljetno kino otvara se večeras.

Because ljetno has to agree with kino.

Kino is a neuter singular noun in the nominative case, so the adjective must also be neuter singular nominative:

• ljetni = masculine
• ljetna = feminine
• ljetno = neuter

So ljetno kino is the correct matching form.

Literally, ljetno kino means summer cinema.

In real usage, it very often refers to a seasonal open-air cinema, because those are common in summer. So depending on context, it may be understood as:

• summer cinema
• open-air cinema
• outdoor cinema

The exact nuance comes from context, not just grammar.

Otvara se means something like opens, is opening, or is being opened, depending on context.

The particle se is very common in Croatian. Here it gives the verb a reflexive/middle sense. It shows that the subject is not actively opening something else; instead, the subject itself is the thing that is opening.

Compare:

• Otvara kino. = He/She is opening the cinema.
• Kino se otvara. = The cinema is opening.

So in this sentence, se helps create the meaning the summer cinema opens / is opening.

Yes, otvara se is grammatically in the present tense.

Croatian often uses the present tense of an imperfective verb for a scheduled or near-future event, especially when there is a time word like večeras.

So although the verb is present in form, the meaning is future in context:

• Ljetno kino otvara se večeras.
• literally: The summer cinema opens tonight.

English does something similar:

• The cinema opens tonight.

So this usage is normal and natural.

This is about aspect, which is very important in Croatian.

• otvarati se = imperfective
• otvoriti se = perfective

The form otvara se comes from otvarati se. It is often used for:

• ongoing situations
• repeated situations
• scheduled events
• general announcements

The form otvori se would come from otvoriti se and usually sounds more like a single completed event viewed as a whole.

In a sentence like this, otvara se večeras is a very natural way to announce that something is opening tonight.

Another possible way to say it would be:

• Ljetno kino otvorit će se večeras.

That is a more explicit future tense.

Yes, Ljetno kino se otvara večeras is also possible.

Croatian word order is more flexible than English word order, especially with short unstressed words like se, which is a clitic. In practice, speakers often use both patterns:

• Ljetno kino otvara se večeras.
• Ljetno kino se otvara večeras.

The meaning stays basically the same. The version with otvara se can sound a bit more polished or written, but both are natural.

Here, večeras is an adverb, meaning tonight or this evening.

So it is not functioning as a noun with a case ending in this sentence. It simply tells you when the opening happens.

You can think of it as answering the question:

• When does it open?
• Večeras.

A native speaker might translate it in a few natural ways, depending on style:

• The summer cinema opens tonight.
• The open-air cinema opens tonight.
• The summer cinema is opening tonight.

All of these fit the Croatian sentence well. English chooses between opens and is opening more by style than by a strict grammar difference here.

Because Croatian normally does not use articles like the and a/an.

So ljetno kino can mean:

• the summer cinema
• a summer cinema

Context tells you which one is meant. In this sentence, if the meaning shown to the learner is the summer cinema opens tonight, that is perfectly normal even though Croatian does not have a separate word for the.

A rough English-friendly pronunciation would be:

LYET-no KEE-no OT-va-ra seh VE-che-ras

A few useful notes:

• lj in ljetno is a soft sound, roughly like ly
• j in Croatian sounds like English y
• č in večeras sounds like ch in church
• e is usually a clear eh sound, not reduced like in English

So:

• ljetno ≈ LYET-no
• kino ≈ KEE-no
• večeras ≈ VE-che-ras