Kalau ruang kelas ini penuh, kita bisa belajar di ruangan sebelah.

Kalau means if in this sentence.

So Kalau ruang kelas ini penuh, ... = If this classroom is full, ...

A few useful notes:

• kalau is very common in everyday Indonesian.
• It can sometimes also mean when depending on context, but here if is the natural meaning.
• A more formal alternative is jika.

So:

• Kalau ruang kelas ini penuh... = everyday, natural
• Jika ruang kelas ini penuh... = a bit more formal

Indonesian often does not use a verb like to be in simple statements.

So:

• ruang kelas ini penuh literally looks like this classroom full
• but it means this classroom is full

This is very normal in Indonesian. The adjective can directly describe the noun without adding is/are.

Other examples:

• Rumah itu besar = That house is big
• Saya sibuk = I am busy

In Indonesian, adjectives usually come after the noun they describe.

So:

• ruang kelas ini penuh = this classroom is full
• ruangan sebelah = the next room / the room next door

This is different from English, where adjectives often come before nouns.

Compare:

• English: big house
• Indonesian: rumah besar

But in this sentence, penuh is not directly inside the noun phrase ruang kelas ini; it works as the predicate adjective: the classroom is full.

In Indonesian, demonstratives like ini (this) and itu (that) usually come after the noun.

So:

• ruang kelas ini = this classroom
• buku itu = that book

This is the normal Indonesian pattern.

Ruang kelas literally means classroom.

Breakdown:

• ruang = space / room
• kelas = class

Together, ruang kelas means classroom.

In many situations, people may also simply say kelas, and from context it can mean either:

• class as a lesson/group, or
• classroom

But ruang kelas makes it very clear that we mean the physical room.

This is a very common learner question.

• ruang = room / space
• ruangan = room, enclosed space

In everyday use, ruang and ruangan are often very similar, and in many contexts both can be translated as room.

In this sentence:

• ruang kelas ini = this classroom
• ruangan sebelah = the room next door

Why the switch? Mostly because both are natural here. Indonesian often allows this kind of variation.

A rough nuance:

• ruang can feel a bit more like space/room
• ruangan can feel a bit more like an enclosed room

But in many real-life sentences, the difference is small.

Indonesian has two common words for we:

• kita = we, including the listener
• kami = we, excluding the listener

In this sentence, kita is used because the speaker includes the person being spoken to:

• kita bisa belajar... = we can study... and you are included

If the speaker meant a group that does not include the listener, they would use kami.

This is an important distinction in Indonesian and often feels unusual to English speakers, because English only has one word: we.

Bisa here means can or be able to.

So:

• kita bisa belajar = we can study / we can learn

It expresses possibility or ability.

Be careful: bisa can also mean venom/poison in other contexts, but that is a completely different meaning. In this sentence, it clearly means can.

It can be translated as either study or learn, depending on context.

• belajar often means to study
• it can also mean to learn

In this sentence, English would most naturally say:

• we can study in the room next door

because the context is being in a classroom.

Useful comparison:

• belajar bahasa Indonesia = learn/study Indonesian
• murid sedang belajar = the students are studying

Because belajar can stand on its own.

So kita bisa belajar already means we can study.

If you want, you can add more information:

• kita bisa belajar di ruangan sebelah = we can study in the room next door
• kita bisa belajar matematika di ruangan sebelah = we can study math in the room next door

So the object is optional when the meaning is already clear from context.

Di ruangan sebelah means in the room next door or in the adjacent room.

Breakdown:

• di = in / at
• ruangan = room
• sebelah = side / next to / beside

So literally it is something like in the room beside [this one].

A very natural English translation is:

• in the next room
• in the room next door

Sebelah relates to side or beside/next to, depending on the structure.

In this sentence:

• ruangan sebelah = the room next door / the adjacent room

You may also see:

• di sebelah = beside / next to
• sebelah kiri = the left side
• sebelah kanan = the right side

So sebelah is a useful word connected to position and neighboring location.

Yes. Indonesian allows flexibility here.

Original:

• Kalau ruang kelas ini penuh, kita bisa belajar di ruangan sebelah.

You could also say:

• Kita bisa belajar di ruangan sebelah kalau ruang kelas ini penuh.

Both mean essentially the same thing:

• If this classroom is full, we can study in the room next door.

Putting the kalau clause first often sounds a bit more organized because it sets up the condition before the result.

Both can work, depending on context.

Penuh literally means full. In a classroom context, that often implies:

• there is no more space, or
• too many people are already inside

So in natural English, you might translate it as:

• If this classroom is full...
• If this classroom is crowded...

But full is the more direct translation.

Yes, there are several natural alternatives.

For example:

• Kalau kelas ini penuh, kita bisa belajar di ruang sebelah.
• Jika ruang kelas ini penuh, kita bisa belajar di ruangan sebelah.
• Kalau ruang kelas ini sudah penuh, kita bisa belajar di ruangan sebelah.

Notes:

• kelas ini may be used instead of ruang kelas ini if the context already makes it clear you mean the classroom.
• jika is more formal than kalau.
• sudah penuh adds the sense of already full.

All of these are natural, with small differences in tone or specificity.

Yes:

• Kalau = if
• ruang kelas ini = this classroom
• penuh = full
• kita = we (including the listener)
• bisa = can
• belajar = study / learn
• di = in
• ruangan sebelah = the next room / the room next door

So the full structure is:

• Kalau ruang kelas ini penuh, = If this classroom is full,
• kita bisa belajar di ruangan sebelah. = we can study in the room next door.