Kamar saya kemasukan air tadi malam karena jendela tidak ditutup rapat.

In Indonesian, air means water, not air in the English sense.

• air = water
• udara = air

So kemasukan air means water got in or the room got water inside, not air got in.

Also, Indonesian air is pronounced roughly ah-eer, so it does not sound like the English word air.

Kemasukan comes from the root masuk (to enter/go in) with the circumfix ke-...-an.

In this kind of sentence, ke-...-an often gives the idea of:

• something happening to someone or something
• often accidentally
• often with an unwanted result

So:

• masuk air = water enters
• kamar saya kemasukan air = my room got water in it / my room was entered by water

This makes kemasukan air sound more natural than just masuk air in this context, because it emphasizes that the room was affected by the water.

You can compare it with similar patterns:

• kecurian = to have something stolen / be robbed
• kehujanan = to get caught in the rain
• kemasukan maling = to have a thief get in

Yes. Kamar saya means my room.

The order is:

• kamar = room
• saya = I / me / my

In Indonesian, possession is often shown by putting the possessor after the noun:

• rumah saya = my house
• buku saya = my book
• kamar saya = my room

So literally it is something like room of mine, but in natural English we say my room.

Tadi malam means last night.

Breakdown:

• tadi = earlier / just now / earlier today, depending on context
• malam = night

Together, tadi malam is a very common expression for last night.

Examples:

• Saya bertemu dia tadi malam. = I met him/her last night.
• Hujan deras tadi malam. = It rained heavily last night.

So in your sentence, it tells you when the water got in.

Indonesian often uses passive constructions when the result or state is more important than who did it.

• jendela tidak ditutup rapat = the window was not closed tightly/properly
• saya tidak menutup jendela = I did not close the window

The sentence you gave focuses on the cause of the problem: the window wasn’t properly shut. It does not need to say who failed to close it.

This kind of passive is very common in Indonesian, especially when:

• the doer is unknown
• the doer is obvious
• the doer is not important
• the speaker wants to focus on the condition or result

The prefix di- usually marks the passive voice in Indonesian.

• menutup = to close
• ditutup = to be closed

So:

• jendela ditutup = the window is closed / was closed

In your sentence:

• jendela tidak ditutup rapat = the window was not closed tightly

This is a very common pattern in Indonesian grammar.

Here, rapat means tight, closely, or properly shut.

So:

• ditutup rapat = closed tightly / shut properly

In this sentence, rapat describes how the window was closed.

A few related examples:

• Pintu ditutup rapat. = The door was shut tightly.
• Tolong tutup botolnya rapat. = Please close the bottle tightly.

Be careful: rapat can also mean meeting as a noun in another context.

• Saya ada rapat. = I have a meeting.

So the meaning depends on context.

Not exactly, though it can be translated that way depending on context.

Kemasukan air literally means:

• had water get in
• got water inside
• was entered by water

It suggests that water came into the room, but it does not always mean a full serious flood. It could be:

• rainwater leaking in
• water seeping in from outside
• water entering through a gap or open window

In English, possible translations include:

• My room got water in it last night...
• Water got into my room last night...
• My room leaked / got flooded last night... — only if the situation was bad enough

So flooded may be too strong in some contexts.

Indonesian does not have articles like the or a/an.

So jendela can mean:

• a window
• the window

The exact meaning depends on context.

In this sentence, English naturally uses the window because the speaker probably means a specific window connected to the room. But Indonesian does not need a separate word for the.

Yes, jendelanya would also be possible in some contexts, but it changes the nuance slightly.

• jendela = window / the window
• jendelanya = the window / his-her-its window / the window in question

The suffix -nya can make something sound more definite or refer back to something known.

So:

• karena jendela tidak ditutup rapat = because the window wasn’t closed tightly
• karena jendelanya tidak ditutup rapat = because the window wasn’t closed tightly / because its window wasn’t closed tightly

Both can work, but the version without -nya is perfectly natural.

Use tidak to negate:

• verbs
• adjectives
• some adverb-like expressions

Use bukan mainly to negate:

• nouns
• noun phrases
• identification/classification

Here, ditutup is a verb form, so you say:

• tidak ditutup = not closed

Not:

• bukan ditutup — this would be wrong in this context

Compare:

• Jendela tidak ditutup. = The window was not closed.
• Itu bukan jendela. = That is not a window.

The sentence is:

Kamar saya kemasukan air tadi malam karena jendela tidak ditutup rapat.

A helpful breakdown is:

• Kamar saya = my room
• kemasukan air = got water in it / had water enter
• tadi malam = last night
• karena = because
• jendela tidak ditutup rapat = the window was not closed tightly

So the overall structure is roughly:

[subject] + [what happened] + [time] + [reason]

That is very normal Indonesian word order.

Yes, you could say Air masuk ke kamar saya tadi malam karena jendela tidak ditutup rapat, and it would be understandable.

But the nuance is a little different:

• Air masuk ke kamar saya = Water entered my room
• Kamar saya kemasukan air = My room got water in it

The version with kemasukan sounds more natural if you want to emphasize that the room was affected by an unwanted event. It often feels more idiomatic in everyday Indonesian for this kind of situation.