Learn Hardcore Indonesian: Dia menambah gula ke kopi agar tidak terlalu pahit. - He/She adds sugar to the coffee so it is not too bitter.

Dia is a third-person singular pronoun meaning “he,” “she,” or “they” (singular). It’s gender-neutral; Indonesian doesn’t mark gender in pronouns. In more formal writing, you might see Ia as a subject pronoun. If you want to specify possession, you can attach -nya to a noun, e.g., kopinya = “his/her coffee.”

Why menambah and not menambahkan? Are both correct?

Both are correct, with a slight nuance:

menambah = to add/increase (focus on the quantity increasing)
menambahkan = to add X to Y (focus on the act of adding something to a target) In this sentence, either Dia menambah gula ke kopi... or Dia menambahkan gula ke (dalam) kopi... works. Other natural options:
Dia memasukkan gula ke dalam kopi. (puts sugar into the coffee)
Colloquial: Dia nambah gula ke kopi.

Is ke kopi natural, or should it be ke dalam kopi or pada kopi?

ke kopi is common and understood in everyday speech.
ke dalam kopi is more precise (literally “into the coffee”).
pada kopi is acceptable in formal writing but sounds stilted in conversation; for physical “into,” ke (dalam) is more natural. Avoid kepada kopi (used for people) and di kopi for movement (use di for location after placement, e.g., menaruh gula di dalam kopi).

What does agar mean, and can I use supaya or biar instead?

agar means “so that/in order that” and introduces a purpose clause. Near-synonyms:

supaya: neutral, very common
biar: informal/colloquial All three fit here: agar tidak terlalu pahit, supaya tidak terlalu pahit, biar tidak terlalu pahit.

Why is there no subject after agar in agar tidak terlalu pahit? Who is “not too bitter”?

Indonesian often omits an obvious subject. Here, the implied subject is the coffee. To be explicit, you can say:

agar kopinya tidak terlalu pahit
agar rasanya tidak terlalu pahit (“so that the taste isn’t too bitter”)

Why tidak and not bukan in tidak terlalu pahit?

Use tidak to negate verbs and adjectives; pahit is an adjective. Use bukan to negate nouns or to correct identification. So tidak terlalu pahit is correct.

How does terlalu work here? Is it the same as “very”?

terlalu means “too/overly (much).” It signals excess, not just intensity. Compare:

sangat pahit = very bitter
terlalu pahit = too bitter (excessive) The pattern is (tidak) terlalu + adjective.

Can I move the purpose clause to the front?

Yes. For example:

Agar tidak terlalu pahit, dia menambah gula ke kopi.
Supaya rasanya tidak terlalu pahit, dia menambahkan gula ke dalam kopi. This is natural; add a comma after the purpose clause.

How do I show past or future time with this sentence?

Indonesian doesn’t inflect verbs for tense. Add time/aspect words:

Past/completed: Dia sudah menambahkan gula ke kopinya agar rasanya tidak terlalu pahit.
Recent past: Tadi dia menambah gula ke kopi...
Future: Dia akan menambahkan gula ke kopi...

How would this sound in casual spoken Indonesian?

Very natural colloquial versions:

Dia nambah gula ke kopi biar nggak terlalu pahit.
Dia nambahin gula ke kopinya biar gak terlalu pahit. Notes: nambah/nambahin (colloquial), biar (informal), nggak/gak (informal “not”).

How can I specify the amount of sugar?

Add a quantity phrase:

Dia menambahkan satu sendok teh gula ke dalam kopi.
Dia menambah sedikit gula ke kopinya.
Dia menambahkan gula secukupnya ke kopi. (an appropriate amount)

Do I need -nya on kopi (e.g., kopinya)?

Not required. Plain kopi is generic (“coffee”). Add -nya to mark specificity/possession:

ke kopinya = to his/her/their coffee, or the mentioned coffee If you want to make the referent explicit in the purpose clause, you can say agar kopinya tidak terlalu pahit or agar rasanya tidak terlalu pahit.