Learn Hardcore Indonesian: Kakek saya pernah menjalani rawat inap tiga hari karena infeksi paru-paru. - My grandfather once underwent three days of inpatient care because of a lung infection.

kakek saya is more neutral and slightly more formal; very common in speech and writing.
kakekku feels a bit more personal/intimate or literary; common in stories, songs, and sometimes casual speech.

In most everyday contexts, you can safely use either one. In formal writing (e.g. medical forms, news), kakek saya is more typical.

What exactly does pernah mean here, and is it necessary? How is it different from sudah or from not using anything?

Pernah marks an experience that happened at least once in the past, without focusing on completion or result. In this sentence:

Kakek saya pernah menjalani rawat inap…
⇒ My grandfather has at some point been hospitalized… (at least once in his life)

If you change it:

Kakek saya sudah menjalani rawat inap…
⇒ Emphasizes that the hospitalization has already taken place (often in contrast to not yet).
Kakek saya menjalani rawat inap… (no marker)
⇒ A simple past statement; context decides the time. Feels more like narrating a specific event.

So:

Use pernah to talk about life experience (ever/has once).
Use sudah to stress already or completion.
Omit both for a neutral past (often clear from context).

In this sentence, pernah is natural but not grammatically required; removing it slightly changes the nuance, not the basic fact.

What does menjalani mean literally? Why not use something like mengalami or just dirawat inap?

Menjalani literally means to go through / undergo / live through (a process or period).

Common collocations:

menjalani operasi – undergo surgery
menjalani perawatan – undergo treatment
menjalani hukuman – serve a sentence
menjalani pemeriksaan – undergo an examination/checkup

Here, menjalani rawat inap ≈ to undergo inpatient care / to be hospitalized.

Alternatives:

mengalami rawat inap – grammatically OK, but less idiomatic. Mengalami is more like to experience (an event/problem); we more often say mengalami kecelakaan, mengalami sakit keras, etc.
dirawat inap – passive: Kakek saya pernah dirawat inap tiga hari… (My grandfather was hospitalized for three days…). This is also natural and common.

So menjalani rawat inap is a natural, slightly formal way to say underwent hospitalization in an active voice.

Is rawat inap a verb or a noun? How does this phrase work grammatically?

Rawat inap is a noun phrase meaning inpatient care / hospitalization.

Breakdown:

rawat – care/treatment (as a root; the verb is often merawat = to care for, treat)
inap – stay overnight (often in a hospital or lodging)

Together rawat inap = the type of care where you stay in the hospital.

In the sentence:

menjalani (verb) + rawat inap (noun phrase)
⇒ to undergo inpatient care / hospitalization

You can treat rawat inap like other nouns:

masa rawat inap – the hospitalization period
biaya rawat inap – hospitalization costs
ruang rawat inap – inpatient ward

Why is tiga hari placed after rawat inap? Could I move it somewhere else?

The default and most natural placement is:

menjalani rawat inap tiga hari
(underwent hospitalization for three days)

You can move tiga hari, but some positions sound more natural than others:

Kakek saya pernah menjalani rawat inap selama tiga hari…
– Adding selama (for) is very natural and clear.
Kakek saya pernah menjalani rawat inap tiga hari karena infeksi paru-paru.
– Original; natural.
Kakek saya pernah tiga hari menjalani rawat inap…
– Possible, but sounds a bit marked/less common in everyday speech.

So the original order is the most typical; Indonesian usually puts the duration after the action or object.

Why is there no word like for before tiga hari? Can I add selama tiga hari? Does it change the meaning?

Indonesian often omits a preposition before a duration; tiga hari alone can mean for three days.

menjalani rawat inap tiga hari
⇒ underwent hospitalization for three days

Adding selama is also correct:

menjalani rawat inap selama tiga hari

Differences:

Meaning: essentially the same in this context.
Nuance: selama makes the duration explicitly marked; it can sound a bit more formal/emphatic or careful.

Both are fine; omitting selama is very common in speech.

What is the function of karena here, and can I switch the order of the clauses like in English?

Karena means because and introduces the cause.

Original:

Kakek saya pernah menjalani rawat inap tiga hari karena infeksi paru-paru.
⇒ He was hospitalized three days because of a lung infection.

You can switch the order, just like in English:

Karena infeksi paru-paru, kakek saya pernah menjalani rawat inap tiga hari.
⇒ Because of a lung infection, my grandfather once underwent three days of hospitalization.

Both are correct. When karena-clause comes first, you usually put a comma after it. The meaning is the same; the change is just emphasis (starting with the cause vs. starting with the person/event).

What does paru-paru literally mean, and why is it reduplicated? Does it mean plural lungs?

Paru-paru is the standard word for lungs.

Root paru is not commonly used alone in everyday modern Indonesian; you normally say paru-paru.
The reduplication here is part of the fixed word, not just a simple plural marker.

So:

paru-paru = lungs (organ)
You don’t say paru for one lung in normal medical or everyday language; you’d still say paru-paru kiri (left lung), paru-paru kanan (right lung).

Reduplication in Indonesian often marks plurality or variety, but in many body-part words it’s just lexicalized (fixed), e.g.:

mata-mata (spy; not eyes)
kuping (ear) vs telinga; no reduplication

In short: treat paru-paru as a single dictionary word meaning lungs.

Why is it infeksi paru-paru and not infeksi di paru-paru? Are both correct?

Both are possible, but they differ slightly in style and nuance:

infeksi paru-paru
– Compact noun phrase (lung infection).
– Feels more medical/technical or formal, like English lung infection or pulmonary infection.
infeksi di paru-paru
– Literally infection in the lungs.
– Slightly more descriptive; common in everyday explanation.

In many contexts they are interchangeable. In a concise sentence like this, infeksi paru-paru is shorter and sounds quite natural, especially when summarizing a diagnosis.

Is the whole sentence formal, informal, or neutral? Where could I use a sentence like this?

The sentence is neutral leaning to slightly formal, mostly because of:

kakek saya (neutral)
pernah menjalani rawat inap (slightly formal/medical)
infeksi paru-paru (technical-ish)

You can use this sentence:

In everyday conversation when telling a story about your grandfather’s health.
In a doctor–patient conversation.
In written forms, medical histories, or reports (though those might be made even more formal).

It’s not slang or childish; it’s appropriate in most situations.

If I want to say that my grandfather has never been hospitalized for a lung infection, how do I negate this sentence correctly?

Use tidak pernah (never) before the verb:

Kakek saya tidak pernah menjalani rawat inap karena infeksi paru-paru.
⇒ My grandfather has never undergone hospitalization because of a lung infection.

Notes:

tidak negates verbs/adjectives;
pernah alone = has ever;
tidak pernah = has never.

If you want to specify the duration too:

Kakek saya tidak pernah menjalani rawat inap tiga hari karena infeksi paru-paru.
⇒ He has never had a three‑day hospitalization due to a lung infection (he might have had shorter/longer ones for that or other reasons, depending on context).

Could I drop saya and just say Kakek pernah menjalani rawat inap tiga hari…? Would it still mean my grandfather?

In many real conversations, yes, people often drop saya when it’s clear from context whose grandfather you’re talking about.

Kakek pernah menjalani rawat inap tiga hari karena infeksi paru-paru.

Depending on context, kakek could mean:

my grandfather
(someone’s) grandfather in general
a generic older man, sometimes

If earlier in the conversation it’s already clear you’re talking about your grandfather, native speakers will understand kakek as my grandfather even without saya.

However, if you need to be clear and explicit (e.g., in writing, forms, or when the context is not obvious), it’s safer to keep kakek saya.