Learn Hardcore Indonesian: Kamar kosmu lebih rapi, dan tikarnya lebih bersih daripada tikarku. - Your boarding room is tidier, and its mat is cleaner than my mat.

kos (also written kost) is the boarding house itself: a place where many people rent rooms.
- Example: Saya tinggal di kos dekat kampus. – I live in a boarding house near campus.
kamar kos is one of the individual rooms in that building.
- Example: Kamar kosmu besar. – Your boarding-house room is big.

So kamar kosmu is “your room in the boarding house,” not the whole boarding house.

What does the -mu at the end of kosmu mean, and where can I put it?

The suffix -mu means “your” (informal, singular or plural) and attaches directly to nouns:

buku → bukumu = your book
rumah → rumahmu = your house
kos → kosmu = your boarding house / your kost

In kamar kosmu, -mu attaches to kos, not to kamar, so the phrase is understood as:

kamar (di) kosmu = “the room (in) your boarding house”

You could also say kamarmu di kos, which would emphasize “your room (which happens to be in a kos),” but kamar kosmu is the more natural compact expression for “your boarding-room.”

Why is it tikarnya and not just tikar for “the mat”?

The suffix -nya on a noun often works like “the” or “that … we already know about”:

tikar = a mat / mats (indefinite)
tikarnya = the mat (the specific mat we’ve been talking about)

So tikarnya lebih bersih means “the mat is cleaner” – we know which mat from context (probably the mat in your room).

-nya can also mean his/her/its/their, but in many sentences (including this one) it just marks a specific, known thing, not a possessor.

How does lebih … daripada … work? Is it just “more … than”?

Yes. The pattern lebih + adjective + daripada + comparison is the basic way to say “more … than …”:

lebih rapi = more tidy / neater
lebih bersih = cleaner
daripada tikarku = than my mat

So:
tikarnya lebih bersih daripada tikarku
= “the mat is cleaner than my mat.”

The normal word order is:

[Subject] + lebih + [adjective] + daripada + [thing it’s compared to]

Can I remove daripada tikarku and just say tikarnya lebih bersih?

Yes, if the comparison is already clear from context.

tikarnya lebih bersih = “the mat is cleaner” (cleaner than what? – understood from context)
tikarnya lebih bersih daripada tikarku = “the mat is cleaner than my mat” (explicit)

In your full sentence, daripada tikarku makes the comparison explicit, which is helpful if it might be ambiguous.

Why is it daripada and not just dari in the comparison?

In comparative sentences with lebih, the standard form is:

lebih + adjective + daripada + noun/pronoun

So: lebih bersih daripada tikarku.

In informal speech, many Indonesians do say lebih … dari …:

lebih bersih dari tikarku

This is common and usually understood, but in careful or formal Indonesian, daripada is preferred for “than” in comparisons.

Why is there no word like “is/are” in this sentence? Where’s the verb?

Indonesian usually does not need a verb like “to be” (is/are) when describing a state with an adjective. The adjective itself functions like the predicate:

Kamar kosmu rapi. – Your room is tidy.
Tikarnya bersih. – The mat is clean.

In comparisons we just insert lebih before the adjective:

Kamar kosmu lebih rapi. – Your room is tidier.
Tikarnya lebih bersih. – The mat is cleaner.

The verb adalah is used in other situations (e.g., linking to a noun phrase: Dia adalah dokter – “He is a doctor”), but not normally before adjectives like rapi or bersih.

Is the comma and dan necessary between the two parts, or could I say this differently?

The sentence:

Kamar kosmu lebih rapi, dan tikarnya lebih bersih daripada tikarku.

Has two coordinated clauses:

Kamar kosmu lebih rapi – your boarding-room is tidier
tikarnya lebih bersih daripada tikarku – and the mat is cleaner than my mat

You have options:

With dan (as given):
Kamar kosmu lebih rapi dan tikarnya lebih bersih daripada tikarku.
(Comma is optional in normal writing.)
More compact, repeating less:
Kamar kosmu dan tikarnya lebih bersih daripada tikarku.
(Here it can be read as “Your room and its mat are tidier/cleaner than mine,” but the exact nuance changes.)

The version with dan tikarnya clearly separates the room and the mat as two things being commented on.

Can rapi and bersih be used for people too, or only for rooms and objects?

Both can be used more broadly:

rapi
- Rooms / things: kamar rapi, meja rapi – tidy
- People’s appearance:
  - Dia sangat rapi. – He/she is very neat (well-dressed, well-groomed).
bersih
- Rooms / things: kamar bersih, baju bersih – clean
- Body / health:
  - Tanganmu bersih. – Your hands are clean.
  - Makanannya bersih. – The food is hygienic / clean.

So they are not limited to rooms, but the meaning remains “tidy” or “clean” in all uses.

Could I say lebih bersih tikarnya instead of tikarnya lebih bersih?

No, that would sound wrong in standard Indonesian.

The usual order is:

[Subject] + lebih + adjective

So:

tikarnya lebih bersih = correct
lebih bersih tikarnya = not natural

You can occasionally front an adjective phrase for emphasis in more literary or stylistic Indonesian, but in everyday speech and writing, keep subject → lebih → adjective.

Why do we say tikarku (“my mat”) at the end? Could we just say daripada tikar?

tikarku makes the comparison personal and specific: compared to my mat.

daripada tikarku = than my mat
daripada tikar = than a mat / than the mat (unclear whose, sounds incomplete)

In this context, the speaker is contrasting your things with my things, so it’s natural to repeat the possessive: tikarku. Dropping -ku would weaken or obscure that contrast.

Is -mu (in kosmu) informal? How would I say this more politely?

Yes, -mu corresponds to kamu and is informal. It’s fine with friends, classmates, roommates, etc.

For more polite or formal speech:

Instead of kamu / -mu, use Anda (you, formal).
There is no -Anda suffix, so you keep Anda as a separate word.

A more formal version could be:

Kamar kos Anda lebih rapi, dan tikarnya lebih bersih daripada tikar saya.

Here:

Anda = you (formal)
saya = I / my (formal)

This sounds more polite and is suitable for speaking to customers, older strangers, or in a formal setting.