Learn Hardcore Indonesian: Saya khawatir infeksi ini belum sembuh. - I am worried this infection has not healed yet.

Saya – neutral and polite. Safe for almost any situation: talking to strangers, teachers, doctors, in writing, etc.
Aku – informal/intimate. Used with close friends, family, people your age (depending on region and relationship).

In Saya khawatir infeksi ini belum sembuh, Saya is a good choice when speaking to a doctor, nurse, or someone you don’t know well. With a close friend, Aku khawatir… would sound more natural.

Can I omit Saya and just say Khawatir infeksi ini belum sembuh?

You can, but it changes the feel:

Saya khawatir infeksi ini belum sembuh. – clear, complete sentence: I am worried…
Khawatir infeksi ini belum sembuh. – sounds more like a fragment or a note to yourself: [I’m] worried this infection hasn’t healed.

In casual speech, people sometimes drop the subject if it’s obvious, but for learners and in careful speech, keep Saya.

Is khawatir a verb or an adjective? Is this “I worry” or “I’m worried”?

In Indonesian, khawatir can behave like both an adjective and a sort of “stative verb” (like takut, marah, sedih).

In English you’d translate Saya khawatir… as I’m worried that…, not I worry that… (which sounds habitual).

Patterns:

Saya khawatir infeksi ini belum sembuh. – I’m worried this infection hasn’t healed.
Saya khawatir tentang infeksi ini. – I’m worried about this infection.
Orang tua saya khawatir. – My parents are worried.

You do not say Saya adalah khawatir.

Why is it infeksi ini and not ini infeksi?

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

infeksi ini – this infection
infeksi itu – that infection
rumah ini – this house
buku itu – that book

Ini infeksi is possible, but it means This is an infection, not this infection.
So:

Infeksi ini belum sembuh. – This infection hasn’t healed.
Ini infeksi. – This is an infection. (identifying what it is)

Why do we use belum instead of tidak before sembuh?

Belum and tidak both negate, but with different meanings:

belum = not yet → suggests it may or is expected to happen later.
tidak = not / does not / is not → simple negation, with no “yet” idea.

So:

Infeksi ini belum sembuh. – This infection hasn’t healed yet. (implies: we expect it might heal)
Infeksi ini tidak sembuh. – This infection does not heal / didn’t heal. (sounds like: it failed to heal, more final)

In your sentence, belum sembuh is natural because healing is a process you expect to complete.

Does belum always carry the idea that it will or should happen later?

Usually belum carries an expectation or at least a possibility that it might happen later, but how strong that feeling is depends on context and tone.

Dia belum datang. – He/She hasn’t come yet. (strong expectation they will)
Penyakitnya belum sembuh. – The illness hasn’t healed yet. (hope/expectation it will)

Sometimes people still use belum even when they’re pessimistic, but the core meaning is “not yet (up to now)” rather than a flat “no”.

Why is there no word for “am” or “is” in Saya khawatir? Why not Saya adalah khawatir?

Indonesian does not use a verb like am/is/are before adjectives or stative words:

Saya khawatir. – I am worried.
Dia sakit. – He/She is sick.
Rumah itu besar. – That house is big.

Adalah is only used:

mainly in more formal or written Indonesian,
to link two nouns, not adjectives:
- Ini adalah rumah saya. – This is my house.
- Dia adalah dokter. – He/She is a doctor.

So Saya adalah khawatir is incorrect.

In English we say “I’m worried that this infection hasn’t healed.” Where is that in the Indonesian sentence?

Indonesian can use bahwa for “that” as a conjunction, but it’s usually optional in everyday speech.

Saya khawatir infeksi ini belum sembuh.
Saya khawatir bahwa infeksi ini belum sembuh.

Both are correct; the first (without bahwa) is more common in conversation. Many verbs of thinking/feeling work this way:

Saya pikir dia sudah pulang. – I think (that) he’s gone home.
Saya takut kamu sakit. – I’m afraid (that) you’re sick.

What exactly does sembuh mean, and how is it used?

Sembuh means to recover / to heal / to get better (from an illness, injury, infection, etc.). It’s intransitive here (no direct object):

Lukanya sudah sembuh. – The wound has healed.
Dia belum sembuh dari flu. – He/She hasn’t recovered from the flu yet.

Related forms:

menyembuhkan – to cure, to heal (someone/something)
- Dokter menyembuhkan pasien. – The doctor cures/heals the patient.
kesembuhan – recovery (noun)
- Kami berdoa untuk kesembuhanmu. – We pray for your recovery.

How would I say “hasn’t healed completely” in Indonesian?

You can modify sembuh:

Saya khawatir infeksi ini belum sembuh sepenuhnya.
Saya khawatir infeksi ini belum benar-benar sembuh.

Both mean roughly: I’m worried this infection hasn’t completely healed.

How do I express past or future time in a sentence like this, since there is no tense?

Indonesian doesn’t change the verb form; it uses time words instead:

Past:
- Tadi saya khawatir infeksi ini belum sembuh. – Earlier I was worried…
- Dulu saya khawatir infeksi ini belum sembuh. – I used to be worried…
Future:
- Besok saya khawatir infeksi ini belum sembuh. – Tomorrow I’ll be worried this infection hasn’t healed. (a bit unusual)
  More natural:
- Saya takut infeksi ini besok belum sembuh. – I’m afraid this infection still won’t have healed by tomorrow.

The verb khawatir itself doesn’t change; time is shown by context words like tadi, kemarin, besok, nanti, etc.

What’s the difference between khawatir and takut? Could I say Saya takut infeksi ini belum sembuh?

Yes, you can say:

Saya takut infeksi ini belum sembuh.

Differences in nuance:

khawatir – worried, concerned, anxious (mental concern)
takut – afraid, scared (stronger emotion, can include fear)

In this medical context:

Saya khawatir infeksi ini belum sembuh. – sounds like a thoughtful worry/concern.
Saya takut infeksi ini belum sembuh. – sounds more emotional, you’re scared it hasn’t healed.

Both are natural; khawatir is slightly more “calmly concerned” and fits very well with doctors and health discussions.

Could I say infeksinya instead of infeksi ini? Is there a difference?

Yes, and there is a nuance difference:

infeksi ini – this infection (pointing to a specific one, maybe identified in context)
infeksinya – the infection / his/her infection / that infection (the -nya can mean “the” or a previously known/possessed one)

In a doctor–patient talk:

Saya khawatir infeksi ini belum sembuh. – I’m worried this infection hasn’t healed. (maybe pointing to a test result or area)
Saya khawatir infeksinya belum sembuh. – I’m worried the infection hasn’t healed (yet). (refers to “the infection we’ve been talking about”)

Both are correct; infeksinya is very natural when both speakers already know which infection they mean.

How would I express a similar idea using masih? Is belum related to masih?

Belum and masih are different but related:

belum – not yet
masih – still

You could say:

Saya khawatir infeksi ini masih ada. – I’m worried this infection is still there.
Saya khawatir infeksi ini masih belum sembuh. – I’m worried this infection still hasn’t healed.

Masih belum emphasizes that despite the time that has passed, the situation is still “not yet”.