Pendengaran Kakek berkurang.

Pendengaran is a noun built from the root dengar, which is related to hearing/listening.

• dengar = hear / listen
• pendengaran = hearing, the sense of hearing

The pattern peN- ... -an often forms nouns. In this case, it gives you the idea of the faculty or function of hearing, not the action to hear.

So pendengaran is not a verb like hear. It is the noun hearing.

Because this sentence is talking about Grandpa’s hearing as a thing, not about the action to hear.

• mendengar = to hear
• pendengaran = hearing

So:

• Kakek mendengar = Grandpa hears / is hearing
• Pendengaran Kakek berkurang = Grandpa’s hearing has declined

A native English speaker may want to use a verb, but Indonesian often uses a noun here, just like English can say his hearing is getting worse.

Indonesian commonly shows possession by putting the possessor after the noun.

So:

• pendengaran Kakek = Grandpa’s hearing
• literally: hearing Grandpa

This is a very normal pattern in Indonesian:

• buku saya = my book
• rumah Ali = Ali’s house
• pendengaran Kakek = Grandpa’s hearing

There is no apostrophe 's like in English.

When a kinship term like Kakek is used like a name or title for a specific family member, it is often capitalized.

So:

• Kakek = Grandpa, used almost like a proper name
• kakek = grandfather, in a general sense

That means:

• Pendengaran Kakek berkurang sounds like Grandpa’s hearing has declined
• Pendengaran kakek berkurang could sound more like the grandfather’s hearing has declined

In real usage, capitalization can vary a little, but this is the basic idea.

Berkurang means to decrease, to become less, or to be reduced.

In this sentence, it describes a change in Grandpa’s hearing: it has gone down or declined.

So depending on context, you could translate it as:

• has decreased
• has declined
• has gotten worse
  especially if the meaning is about hearing ability

It is an intransitive verb, so it does not take a direct object here.

Kurang and berkurang are related, but they are not the same.

• kurang = less, lacking, insufficient
• berkurang = to decrease, to become less

So berkurang emphasizes a process or change.

Compare:

• Pendengaran Kakek kurang baik = Grandpa’s hearing is not very good
• Pendengaran Kakek berkurang = Grandpa’s hearing has decreased / declined

In your sentence, berkurang is better because it suggests that the hearing used to be better and has now become weaker.

Indonesian often does not need a separate word like is, are, or has where English does.

Here, berkurang already works as the predicate of the sentence, so the sentence is complete without any extra verb.

That is why Indonesian can say simply:

• Pendengaran Kakek berkurang

And English may translate it in different ways depending on context:

• Grandpa’s hearing has declined
• Grandpa’s hearing is reduced
• Grandpa’s hearing is getting worse

So nothing is missing in Indonesian.

Yes, it is grammatical and natural, especially in neutral or somewhat formal language.

It sounds a bit more like written or careful speech than very casual conversation. In everyday speech, people might also say things like:

• Pendengaran Kakek menurun.
• Kakek mulai susah mendengar.

These alternatives are also natural, but the original sentence is perfectly fine.

Yes. Kakek pendengarannya berkurang is also natural.

This version puts Kakek first and uses pendengarannya, which includes -nya. In this kind of sentence, -nya often helps mark something like his hearing or the hearing in question.

So:

• Pendengaran Kakek berkurang = Grandpa’s hearing has declined
• Kakek pendengarannya berkurang = Grandpa, his hearing has declined / Grandpa’s hearing has declined

The meaning is very close. The second version can sound a bit more conversational.

In many Indonesian words, ber- helps form an intransitive verb. It often gives a sense like to have, to wear, to do, or to undergo/be in a state depending on the word.

With kurang, it forms:

• kurang = less / lacking
• berkurang = to become less / to decrease

So in this word, ber- helps turn the idea of less into the verb decrease.

It is best not to force one single English meaning for ber- in every word, because its effect depends on the base word. Here, the safest understanding is simply that berkurang is the verb to decrease.