Learn Hardcore Indonesian: Menurut saya, perabot di apartemen itu sudah lengkap. - In my opinion, the furniture in that apartment is already complete.

Menurut saya = according to me; neutral and slightly formal, often used to frame an opinion politely.
Saya pikir = I think; more cognitive, casual–neutral.
Saya rasa = I feel/I reckon; slightly more subjective/feeling-based.
Informal variant: menurutku (using -ku, intimate/casual).

Is the comma after menurut saya required, and can I move that phrase?

The comma is optional but common. You can place the phrase at the end or in the middle for emphasis:

Menurut saya, perabot di apartemen itu sudah lengkap.
Perabot di apartemen itu sudah lengkap, menurut saya.
Perabot di apartemen itu, menurut saya, sudah lengkap.

What’s the difference between perabot, perabotan, furnitur, and mebel?

Perabot: furniture (individual items or furniture in general).
Perabotan: furnishings/household items as a set/category; often more collective (e.g., toko perabotan).
Furnitur: furniture (loanword; common in media/ads).
Mebel: furniture (older/industry term; you’ll see toko mebel). Not the same as peralatan (equipment), perlengkapan (supplies), or perkakas (tools).

Is perabot singular or plural? How do I say “pieces of furniture”?

Indonesian usually doesn’t mark plural; perabot can mean furniture in general or multiple items. To make plurality explicit:

Reduplication: perabot-perabot (emphatic/many items; not always necessary).
Quantifiers: banyak perabot (a lot of furniture), beberapa perabot (several items).
Classifiers: satu set perabot (a set of furniture), or name the items (sebuah kursi, sebuah meja).

Why is it apartemen itu and not itu apartemen?

Indonesian demonstratives typically follow the noun: noun + itu/ini. So apartemen itu = that apartment. Fronted forms like itu apartemen are rare and used for strong emphasis or in certain constructions.

What does sudah add here, and can I drop it?

Sudah marks that something is already in a certain state. Perabot … sudah lengkap means the furnishings have reached completeness. Without sudah, lengkap is still grammatical but feels more like a timeless description; with sudah it sounds like an assessment or update. Formal: telah; colloquial: udah.

How is lengkap different from penuh, cukup, or komplet/komplit?

Lengkap: complete (nothing missing).
Penuh: full (space is filled, not necessarily complete set).
Cukup: enough/sufficient.
Komplet/komplit: near-synonym of lengkap; komplit is informal spelling.

Is there a more natural way to say “fully furnished”?

Common, natural options:

Apartemen itu perabotnya sudah lengkap.
Apartemen itu sudah lengkap perabotannya.
Formal/standard: Apartemen itu berperabot lengkap. In ads, you’ll also see English mixing: Apartemen itu fully furnished.

Can I use -nya instead of di apartemen itu?

-nya often marks possession/topic: Apartemen itu perabotnya sudah lengkap = the apartment’s furniture is complete. Your original perabot di apartemen itu is also correct; -nya just ties the furniture more tightly to the apartment.

Can I say tersebut instead of itu?

Yes, tersebut is more formal and refers back to something previously mentioned in text/speech: perabot di apartemen tersebut. Itu is neutral and very common in speech.

Why use di and not pada here?

For physical location, Indonesian uses di: di apartemen itu. Pada is more formal/abstract and not used for simple physical location like this.

How do I say it’s not complete yet vs. simply not complete?

Not yet complete: belum lengkap.
Not complete (no implication it will be later): tidak lengkap. Example: Menurut saya, perabot di apartemen itu belum lengkap.

Any tips on pronunciation for perabot and apartemen?

perabot: pe-RA-bot (clear vowels; rolled/flapped r).
apartemen: a-par-te-men (all vowels pronounced; stress tends to be even or penultimate).

What are casual vs. polite ways to express the same idea?

Polite/neutral: Menurut saya, perabot di apartemen itu sudah lengkap.
Casual: Menurutku, perabot di apartemen itu udah lengkap.
Very casual: Kayaknya perabot di apartemen itu udah lengkap deh. (kayaknya = it seems; deh softens the tone).