Learn Hardcore Indonesian: Kausmu kotor; sebaiknya masukkan ke keranjang cucian. - Your T-shirt is dirty; you should put it into the laundry basket.

The suffix -mu is a clitic meaning your (2nd person, usually singular). It attaches to a noun: kausmu = your shirt/T‑shirt. It’s neutral to informal and sounds personal. Alternatives:

kaus kamu: also your (neutral), a bit more explicit/less attached.
kaus Anda: your (formal/polite; capitalize Anda).
Speaking to a group: kaus kalian. The suffix -mu itself isn’t used for plural you.

Is kaus the same as baju or kaos?

kaus: standard word for T‑shirt (KBBI-preferred spelling).
kaos: very common colloquial spelling; widely used in daily life.
baju: general word for clothing/top; could be any shirt.
kemeja: collared shirt, not a T‑shirt. In the given sentence, kausmu most naturally means your T‑shirt, but many speakers would say baju in casual speech if the exact type isn’t important.

Why is there no word for is in Kausmu kotor?

Indonesian doesn’t use a linking verb with adjectives. You simply put the subject and adjective together: Kausmu kotor = Your shirt is dirty. Don’t use adalah before adjectives. For negation, use tidak: Kausmu tidak kotor.

Is the semicolon natural here? Could I use a period or a comma?

Yes, the semicolon is fine in formal writing to join closely related independent clauses. In everyday text, a period is most common:

Kausmu kotor. Sebaiknya masukkan ke keranjang cucian. A comma alone is less standard unless you add a connector:
Kausmu kotor, jadi sebaiknya masukkan ke keranjang cucian.

What does sebaiknya mean exactly? How strong is it?

sebaiknya means it would be better/you’d better; it gives advice, milder than a command.

Stronger: harus (must), wajib (obligatory).
Similar/softer: lebih baik, ada baiknya (it’s better/it would be good if).
Colloquial: mending (better). You can say Sebaiknya kamu masukkan… or, as in the sentence, omit the subject for a general suggestion.

Why masukkan and not memasukkan or just masuk?

masuk = to enter/go in (intransitive).
masukkan = to put something into (transitive; root masuk
- suffix -kan). This is the normal imperative form: Masukkan …
memasukkan is the non-imperative active form: Saya memasukkan baju ke keranjang. Spelling tip: masukkan (two k’s) is the verb. masukan (one k) is a noun meaning input/feedback.

Where is the object of masukkan? Isn’t something missing?

It’s understood from context (the shirt just mentioned). Indonesian often drops objects when they’re obvious. If you want to state it, use:

Sebaiknya masukkan kausmu ke keranjang cucian.
or Sebaiknya masukkan itu ke keranjang cucian.

What’s the difference between masukkan ke and taruh di?

masukkan ke emphasizes moving something into/inside a container: Masukkan … ke keranjang.
taruh di means place/put on or in a location: Taruh di keranjang. Both are fine here; masukkan ke highlights the into aspect. With taruh, use di; with a motion verb, use ke.

Can I say Sebaiknya dimasukkan ke keranjang cucian?

Yes. That’s passive/impersonal and sounds softer or more instructional: It would be best if it were put into the laundry basket. Very natural with tolong:

Tolong, sebaiknya dimasukkan ke keranjang cucian. For a direct request, active Masukkan … is fine.

Would ke dalam be better than ke here?

Both work:

ke keranjang cucian is already understood as into the basket.
ke dalam keranjang cucian adds into the inside explicitly. Use ke dalam if you want to emphasize inside vs. just to the basket’s general area.

Is keranjang cucian the normal way to say laundry basket? Any other options?

Yes, it’s common. Other natural options:

keranjang baju kotor / keranjang pakaian kotor
tempat cucian (general place for laundry)
Colloquial borrowing: keranjang laundry All are widely understood; pick based on style and region.

How can I make the instruction more polite or softer?

Add tolong: Tolong masukkan ke keranjang cucian.
Use silakan when giving permission/inviting: Silakan masukkan …
Add softeners like ya or dong in casual speech: Masukin ke keranjang baju kotor ya.
Use formal address: Bapak/Ibu, sebaiknya kaus Anda dimasukkan ke keranjang cucian.

How do I negate the command?

Use jangan + verb:

Jangan masukkan ke keranjang cucian. To soften: Jangan dulu dimasukkan, ya.

Any pronunciation tips for these words?

kaus: two sounds with the diphthong au like ow in now.
masukkan: pronounce the double k clearly (masuk-kan).
c in cucian is like ch in church.
ng in keranjang is the velar nasal as in sing. Stress is generally even; don’t over-stress syllables as in English.

Is kausmu one word or two? Do I need a hyphen?

Write it as one word without a hyphen: kausmu. The possessive clitics -ku and -mu attach directly to the noun. Use spacing only when kamu/Anda are separate words: kaus kamu, kaus Anda.

How do I talk about plural you or multiple shirts?

Talking to several people: kaus kalian (your shirts, you plural). You can omit plural marking if context is clear.
To mark multiple items explicitly, reduplicate the noun: kaus‑kaus kalian. In casual speech, many just say kaus kalian and rely on context.