Learn Hardcore Malay: Dalam siaran malam itu, doktor ulang bahawa yang paling penting ialah minum air yang cukup setiap hari. - In that evening broadcast, the doctor repeats that the most important thing is to drink enough water every day.

So doktor ulang bahawa… is a slightly more compact, less formal way of saying the same thing. It is still very understandable and fairly natural in many contexts (e.g. news voice-over, captions, casual narrative), but in very formal writing, doktor mengulangi bahawa… would be more textbook-standard.

What is the function of bahawa here? Could we leave it out?

bahawa is a conjunction that introduces a content clause, similar to English that in:

He repeated *that the most important thing is …*

So in:

doktor ulang bahawa yang paling penting ialah …

bahawa marks the beginning of what the doctor repeated: yang paling penting ialah minum air …

In spoken Malay, especially when the clause is long, bahawa is sometimes omitted:

doktor ulang yang paling penting ialah minum air yang cukup setiap hari

This is understandable, especially with a pause before yang paling penting.
However:

In careful or formal written Malay, bahawa is preferred.
It makes the sentence structure clearer, especially for complex content clauses.

So: yes, it can be dropped in informal speech, but it is good practice to keep it in writing and when you want to sound formal or precise.

Why do we say yang paling penting instead of just paling penting?

paling penting by itself means most important as an adjective phrase.

yang in Malay often does two things:

It introduces relative clauses.
It can turn an adjective phrase into a noun-like expression (nominalisation).

Here, yang paling penting literally means that which is most important or the one that is most important, which we usually translate as the most important thing.

So:

paling penting – (is) most important
yang paling penting – the most important one / thing / point

Because the sentence wants to talk about the most important thing as a topic, it needs the yang to make it into a noun phrase that can be the subject:

Yang paling penting ialah … – The most important thing is …

What does ialah do here, and how is it different from adalah? Could we omit it?

ialah is a copular word, roughly like is / are linking two parts of the sentence.

In:

yang paling penting ialah minum air yang cukup setiap hari

it links:

subject: yang paling penting – the most important thing
complement: minum air yang cukup setiap hari – drinking enough water every day

Traditional grammar advice often says:

use ialah when the complement is a noun phrase
use adalah when the complement is an adjective or prepositional phrase

In real usage, people mix them quite a lot, but in this sentence ialah is very natural because minum air yang cukup setiap hari behaves like a noun phrase (like English drinking enough water every day).

Could you omit ialah? In very casual speech, yes:

yang paling penting, minum air yang cukup setiap hari

This becomes more like: the most important thing – drink enough water every day (a looser structure). For clear, neutral Malay, especially in writing, it is better to keep ialah here.

Why is the verb minum in base form and not meminum?

In modern Malay:

minum – to drink (this is the normal everyday form)
meminum – exists, but is limited and feels formal/technical; often used when you want to emphasise causing someone to drink or in older/very formal styles.

Most verbs that take a direct object use the meN- form in neutral prose (makan → memakan, baca → membaca).
However, some very common verbs often appear in root form even when there is an object, and minum is one of them:

minum air – drink water (normal)
makan nasi – eat rice (normal)

So in contemporary standard Malay, minum air is more natural than meminum air. The sentence is using the normal, everyday form.

Why is it air yang cukup, not cukup air or air cukup? What is the difference?

All of these can appear in Malay, but they have slightly different structures and nuances.

air yang cukup
- literally: water that is enough
- yang cukup is a relative clause describing air
- here it means a sufficient amount of water / water in sufficient quantity
- in this sentence: minum air yang cukup ≈ drink enough water
cukup air
- literally: enough water
- cukup is quantifying air (like English enough before a noun)
- minum cukup air is also natural and means essentially the same: drink enough water
- some speakers find minum cukup air a bit more direct in focusing on the quantity.
air cukup
- usually means the water is enough / sufficient (a statement about the water, not an instruction)
- or in some contexts, could be part of a longer phrase (air cukup bersih – water is clean enough).

In this sentence, minum air yang cukup and minum cukup air are both acceptable.
air yang cukup sounds slightly more formal or “complete” because of yang, but the meaning here is the same: drink enough water.

Where can setiap hari go in the sentence? Can we move it earlier?

setiap hari means every day. In Malay, time expressions are quite flexible in position.

Current version:

… minum air yang cukup setiap hari.

This is very natural: drink enough water every day.

You could also say:

… minum air yang cukup pada setiap hari. (more formal, with pada)
… setiap hari minum air yang cukup. (emphasises every day)
Setiap hari, doktor ulang bahawa … (changes the meaning to Every day, the doctor repeats that … – so be careful what it attaches to)

For this exact meaning (the drinking happens every day), the most usual positions are:

minum air yang cukup setiap hari
minum air yang cukup pada setiap hari (formal)

Putting setiap hari where it is now is standard, natural, and clear.

What is the role of itu in malam itu, and why does it come after malam?

itu is a demonstrative, roughly that in English. It marks something specific, already known in the context.

Malay word order in noun phrases is usually:

[head noun] [modifiers] [demonstrative]

So:

malam – night / evening (head noun)
itu – that (demonstrative)

→ malam itu – that night / that evening

Similarly:

buku itu – that book
rumah besar itu – that big house

It is normal in Malay for itu to follow the noun (and most modifiers), whereas in English that normally comes before the noun.

In the sentence, malam itu is part of siaran malam itu:

siaran – broadcast
malam itu – (of) that night
siaran malam itu – the broadcast of that night / that night’s broadcast

Does dalam siaran malam itu mean “in that night’s broadcast” or “during the broadcast that night”, or is there a difference?

In practice, dalam siaran malam itu can be understood both ways, and the difference is very small:

in that night’s broadcast – emphasises the specific programme
during the broadcast that night – emphasises the time (that night)

Grammatically, dalam is linking to siaran (broadcast), and malam itu pinpoints which broadcast. So the core meaning is:

in the broadcast that was on that night

Both English renderings are fine translations of the Malay phrase in this context.

Why is there no pronoun like dia after bahawa (for example, “that he says…”)? Could we put one?

In the sentence:

doktor ulang bahawa yang paling penting ialah minum air yang cukup setiap hari.

the clause after bahawa is general advice, not something that the doctor personally does. It is:

yang paling penting ialah minum air yang cukup setiap hari
→ the most important thing is to drink enough water every day.

If you added dia:

… bahawa dia yang paling penting … – would mean roughly that he is the most important one, which is wrong here.
… bahawa dia perlu minum air yang cukup setiap hari – that he needs to drink enough water every day (different meaning: about him personally).

So there is no pronoun because the clause is not about him or someone specific; it is a general statement.
You could add other subjects if you changed the meaning, for example:

doktor ulang bahawa kita mesti minum air yang cukup setiap hari
→ the doctor repeated that we must drink enough water every day.

What level of formality is this sentence, and how might it change in more casual speech?

The sentence is in neutral to slightly formal standard Malay:

It uses bahawa, yang paling penting, ialah – structures typical of news, articles, or official information.
Vocabulary is standard and clear.

In more casual spoken Malay, people might say something like:

Dalam siaran malam itu, doktor ulang yang paling penting, minum air cukup tiap-tiap hari.
(dropping bahawa and ialah, using tiap-tiap and maybe cukup instead of yang cukup)

Or even shorter:

Masa siaran malam tu, doktor ulang: yang paling penting, kena minum cukup air tiap-tiap hari.

Changes you might see in casual speech:

dalam siaran malam itu → masa siaran malam tu
bahawa often dropped
ialah dropped, replaced by a pause or adalah in some dialects
setiap hari → tiap-tiap hari or just hari-hari

But for learning standard Malay, the original sentence is a good, clean model.