Learn Hardcore Malay: Saya mesti pakai topeng, kalau tidak hidung saya mudah sakit ketika jerebu. - I must wear a mask, otherwise my nose easily hurts during haze.

mesti – strong necessity/obligation, often based on rules, logic, or personal decision.
perlu – need to, focuses on necessity (often more neutral, less “commanding”).
harus – must / should, common in Indonesia; in Malaysia it can sound a bit more formal.
patut – ought to / should, weaker, more about what is appropriate or advisable.

In everyday Malaysian speech, mesti is very common and natural for “must / have to”.

Why is pakai used instead of memakai? Are pakai and memakai interchangeable?

Both pakai and memakai mean to wear / to put on / to use, and in many contexts they are interchangeable.

Saya mesti pakai topeng.
Saya mesti memakai topeng.

Both are correct and mean the same thing.

Nuance:

pakai – shorter, more colloquial, very common in speech.
memakai – slightly more formal, common in writing, speeches, or careful speech.

In normal conversation, pakai is usually preferred:

pakai baju – wear clothes
pakai kasut – wear shoes
pakai topeng – wear a mask

Is topeng the usual word for a medical mask, or does it mean a costume mask?

Traditionally, topeng means mask in a general sense, especially:

costume masks
performance masks
masks that cover the face

In everyday Malaysian usage today:

People do say topeng for a face mask, but more precise/official terms exist:
- pelitup muka – face mask (very common in formal/health contexts, e.g. COVID notices)
- mask / masker – English/borrowed forms often heard in casual speech
- topeng muka – literally face mask; also used, but sounds a bit less formal than pelitup muka.

In this sentence, topeng is understandable and natural in general conversation. If you were writing a health notice, you’d more likely see:

Saya mesti memakai pelitup muka…

What exactly does kalau tidak mean? Is it “if not” or “otherwise”? Can I say jika tidak or kalau tak?

In this sentence, kalau tidak works like English otherwise or if not:

Saya mesti pakai topeng, kalau tidak hidung saya mudah sakit…
≈ I must wear a mask, otherwise my nose easily gets sore…

Details:

kalau tidak – common in speech and writing, neutral in tone.
jika tidak – a bit more formal; used in writing, instructions, official texts.
kalau tak – informal/colloquial version used in conversation (especially in Malaysia).

All of these can fit the same structure:

Saya mesti pakai topeng, kalau tidak…
Saya mesti pakai topeng, jika tidak…
Saya mesti pakai topeng, kalau tak…

The comma before kalau tidak is natural, because it separates the main clause from the consequence.

How should I understand hidung saya mudah sakit? Why is mudah there?

Literally:

hidung saya – my nose
mudah – easy(ly) / tends to
sakit – hurt / painful / sore

So hidung saya mudah sakit means:

My nose easily gets sore / is easily irritated / tends to hurt.

The word mudah here doesn’t mean “easy” in the sense of “not difficult”; it means:

easily / prone to / tends to

This is a common pattern:

kulit saya mudah alergi – my skin easily gets allergic / is allergy-prone
dia mudah penat – he/she easily gets tired
bunga ini mudah layu – this flower easily withers

Without mudah, hidung saya sakit would mean my nose is sore (a simple statement of fact, not about tendency).

If mudah literally means “easy”, why not use senang here? What’s the difference between mudah and senang?

Both mudah and senang can mean easy, but they differ in usage:

mudah:
- “easy” in the sense of not difficult:
  - soalan ini mudah – this question is easy
- also used to mean easily / prone to / tends to (as in our sentence):
  - hidung saya mudah sakit – my nose easily gets sore
senang:
- “easy / simple / convenient” in a more casual sense:
  - kerja ini senang – this job is easy
- also comfortable / at ease / relaxed:
  - saya rasa senang di sini – I feel comfortable here
- not usually used for “prone to” in this medical/physical sense.

So:

hidung saya mudah sakit – natural and correct
hidung saya senang sakit – understandable, but sounds off/nonnative; people don’t usually say it this way.

For “easily gets [state] / prone to [state]”, mudah (and often cepat) is preferred:

hidung saya cepat sakit – my nose quickly / easily gets sore (also natural).

Why is it hidung saya, not saya hidung? How does possession work here?

In Malay, the usual order for possession is:

[noun] + [possessive pronoun]

So hidung saya literally is nose my → my nose.

Other examples:

rumah saya – my house
kereta kamu – your car
buku dia – his/her book

You cannot say saya hidung to mean my nose; saya in front of a noun is usually just I / me as the subject:

saya hidung sakit – incorrect
saya sakit hidung – means I have a nose-ache / my nose hurts, but the structure is different (subject saya, predicate sakit hidung).

You can also say:

hidung saya mudah sakit – my nose easily gets sore
saya mudah sakit hidung – I easily get a sore nose

Both are understandable, but the given sentence focuses on the nose as the subject.

Could this be hidung saya akan mudah sakit? When do I use akan?

Yes, you can say:

Saya mesti pakai topeng, kalau tidak hidung saya akan mudah sakit ketika jerebu.

Akan is a future marker, roughly will.

Nuance:

Without akan:
- hidung saya mudah sakit – can be a general tendency (habit, fact) or a predictable result. Context decides.
With akan:
- hidung saya akan mudah sakit – emphasizes the future result (what will happen if you don’t wear a mask).

In the original sentence, the meaning “otherwise my nose (tends to / will) easily get sore” is already clear without akan, so it’s not required. Malay often omits tense markers unless emphasizing time.

What does ketika mean here? Is it more like “when” or “during”? Can I use masa, semasa, or apabila instead?

Ketika here can be understood as either when or during:

ketika jerebu – when there is haze / during a haze

It often introduces a time phrase or clause:

ketika kecil – when (I was) small
ketika hujan turun – when it rains

Alternatives:

semasa jerebu – during the haze (quite close to ketika, slightly more formal/written)
masa jerebu – during haze / when it’s hazy (more colloquial)
apabila jerebu – when there is haze (often with a full clause after it: apabila jerebu berlaku – when haze occurs)

You could say:

…hidung saya mudah sakit ketika jerebu.
…hidung saya mudah sakit semasa jerebu.
…hidung saya mudah sakit masa jerebu. (very conversational)

All are acceptable; ketika and semasa feel a bit more neutral/formal than masa.

What exactly is jerebu? Is it the same as fog or smoke (kabut, asap)?

Jerebu specifically means haze—reduced visibility caused by fine particles in the air, often from forest fires, pollution, etc.

Related words:

asap – smoke (from fire, cigarettes, etc.)
kabut – fog / mist (from water droplets, like natural fog in cold mornings)
jerubu / jerebu – standardized as jerebu in modern Malay; environmental haze

So during regional forest fires in Southeast Asia, the word you see in the news is usually jerebu, not kabut or asap.

Is this sentence formal, informal, or neutral? How would it sound in casual spoken Malay?

The original sentence is quite neutral—fine for everyday conversation and also acceptable in semi-formal writing.

In very casual Malaysian speech, you might hear:

Aku kena pakai mask, kalau tak hidung aku cepat sakit masa jerebu.

Changes:

Saya → aku (familiar/informal I)
mesti → kena (colloquial “have to / must”)
topeng → mask (English loan in speech)
kalau tidak → kalau tak
mudah sakit → cepat sakit (also “easily / quickly gets sore”)
ketika jerebu → masa jerebu

For formal writing (e.g. health brochure), you might see:

Saya perlu memakai pelitup muka, jika tidak hidung saya mudah terjejas ketika jerebu.

Is the structure of the whole sentence like English, or is the word order different?

The overall structure is quite similar to English:

Saya mesti pakai topeng,
– Subject (Saya) + modal (mesti) + verb (pakai) + object (topeng)
– I must wear a mask,
kalau tidak hidung saya mudah sakit ketika jerebu.
– Connector (kalau tidak) + subject (hidung saya) + adverb (mudah) + predicate/adjective (sakit) + time phrase (ketika jerebu)
– otherwise my nose easily gets sore during haze.

So word order is mostly:

Subject → (modal) → verb → object
Connector → subject → adverb → predicate → time expression

There is no inversion like in English “Otherwise, my nose will easily get sore” vs “My nose will easily get sore, otherwise…”; kalau tidak simply starts the second clause.