Radio itu rusak.

In Indonesian, you often do not need a verb like is / am / are when linking a subject to an adjective or noun.

So:

• Radio itu rusak = The/That radio is broken
• literally, it is more like radio that broken

This is completely normal in Indonesian.
If the predicate is an adjective like rusak (broken, damaged), no separate word for is is needed.

You may sometimes see adalah, but that is usually used in more formal contexts and typically with nouns, not simple adjective statements like this one.

Itu usually means that, but in many sentences it can also function a bit like the in English, depending on context.

So radio itu can mean:

• that radio
• the radio

In natural Indonesian, itu often helps identify a specific thing already known in the conversation.

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

So:

• radio itu = that radio
• buku ini = this book
• rumah itu = that house

This is different from English, where this/that comes before the noun.

In this sentence, rusak works like an adjective, meaning broken or damaged.

So:

• Radio itu rusak = The radio is broken

But Indonesian words can be flexible. Depending on context, rusak can also behave more verbally, especially in expressions related to becoming damaged or being in a damaged state.

For a beginner, the safest way to understand it here is:

• rusak = broken / damaged

Yes. Rusak is a broad word.

It can describe something that is:

• broken
• damaged
• not working properly
• defective

So for a radio, rusak could mean:

• physically broken
• not functioning
• out of order

The exact nuance depends on context.

Yes, Radio rusak is possible, but it feels less specific.

Compare:

• Radio rusak = A radio is broken / The radio is broken / Radio is broken
  
  • more general or context-dependent
• Radio itu rusak = That radio / the radio is broken
  
  • points to a specific radio

Adding itu makes the reference clearer.

No. Indonesian nouns usually do not change form for singular and plural.

So radio can mean:

• radio
• radios

If you need to make plurality clear, Indonesian often uses context, numbers, or reduplication:

• satu radio = one radio
• dua radio = two radios
• radio-radio = radios

But in your sentence, radio is understood as singular from context.

Usually, the most natural meaning is That radio is broken.

If you want to emphasize an event in the past, like That radio broke, Indonesian would often use extra context, such as time words:

• Radio itu tadi rusak = That radio broke earlier / was broken earlier
• Radio itu sudah rusak = That radio is already broken / has become broken

Without extra markers, Radio itu rusak is most naturally understood as describing its current state.

A simple approximation is:

• RAH-dee-oh EE-too ROO-sak

A few notes:

• r in Indonesian is usually rolled or tapped
• u is like oo in food
• a is usually like a in father
• stress is not as strong as in English

More roughly:

• radio → rah-dee-o
• itu → ee-too
• rusak → roo-sak

No, that would sound unnatural.

Adalah is generally not used before adjectives like rusak in a simple sentence.

Natural:

• Radio itu rusak

Unnatural:

• Radio itu adalah rusak

Use adalah mostly in more formal definitions or identifications, especially with nouns:

• Ini adalah radio baru. = This is a new radio.
• Dia adalah guru. = He/She is a teacher.

But with adjective predicates like rusak, just leave it out.

The basic pattern here is:

• [noun] + itu + [adjective]

So yes, for a sentence like this, that pattern is very common:

• Mobil itu mahal = That car is expensive
• Rumah itu besar = That house is big
• Radio itu rusak = That radio is broken

More broadly, the structure is:

• subject + predicate

And when the subject includes itu, it usually follows the noun:

• buku itu
• anak itu
• radio itu

So the full sentence structure is very natural Indonesian.