Learn Hardcore Indonesian: Aku tertawa karena komentar teman itu lucu. - I laugh because that friend’s comment is funny.

aku: informal/neutral; use with friends, family, peers.
saya: polite/formal; use with strangers, at work, in writing. Very casual in Jakarta: gue. The rest of the sentence can stay the same.

What’s the difference between tertawa and ketawa?

Both mean “to laugh.”

tertawa: standard/neutral; good for writing and speech.
ketawa: colloquial; very common in casual speech. You can intensify: tertawa terbahak-bahak (laugh out loud), tertawa kecil (chuckle).

Why is there no “to be” before lucu? Should it be adalah?

Indonesian adjectives can be predicates, so lucu stands alone: komentar … lucu.
adalah is typically used when the predicate is a noun phrase, not an adjective, so komentar itu adalah lucu sounds unnatural. For emphasis, use particles like memang or sangat: komentar itu memang lucu.

What exactly does komentar teman itu mean? Does itu modify teman or komentar?

It means “that friend’s comment.” Breakdown:

komentar = comment
teman itu = that friend
So itu modifies teman, not komentar. If you want “that comment,” say komentar itu.

Could I say komentarnya lucu instead?

Yes. -nya makes the noun definite and can also mark a third-person possessor.

Komentarnya lucu = “The comment was funny” or “His/Her comment was funny” (context decides).
To keep “that friend” explicit: komentar teman itu lucu. With -nya: komentar temannya lucu = “the friend’s comment,” but the owner is only understood from context.

Is teman singular or plural here? How do I say “friends”?

It’s number-neutral; context decides. To mark plural, reduplicate: teman-teman = friends.
“Those friends” = teman-teman itu.
Note: para is a formal plural marker used with groups like para siswa (students), para tamu (guests), and is not common with teman.

Can I put the because-clause first? Do I need a comma?

Yes: Karena komentar teman itu lucu, aku tertawa.
When the karena-clause comes first, use a comma. When it follows the main clause, a comma is usually not used: Aku tertawa karena komentar teman itu lucu.

Can I just say Aku tertawa karena lucu?

In casual speech, yes—listeners infer what “is funny” from context. In careful or written Indonesian, karena normally introduces a full clause, so it’s clearer to say Aku tertawa karena komentar teman itu lucu or Aku tertawa karena itu lucu if the referent is obvious.

Are there other ways to say “because” besides karena? How do sebab, gara-gara, soalnya, lantaran differ?

sebab: also “because”; a bit more formal/bookish. Works here: Saya tertawa sebab …
gara-gara: “because of,” often with a negative/annoyed nuance (blaming a cause). Not ideal for a positive cause like something being funny.
soalnya: very casual, literally “the reason is.” Often after a pause/comma: Aku tertawa, soalnya komentar teman itu lucu.
lantaran: less common; literary/regional; similar to karena.
Note: oleh karena itu means “therefore,” not “because.”

What does the -ter- in tertawa do? Should I ever say bertertawa?

Here tertawa is a fixed verb meaning “to laugh”; the ter- doesn’t carry its usual “accidental/state/superlative” meanings. Don’t say bertertawa. Related forms:

tawa (noun: laughter)
ketawa (colloquial verb)
tertawa terbahak-bahak (laugh out loud)

Is teman itu the same as teman yang itu?

Not exactly:

teman itu: “that friend” (already known or contextually identifiable).
teman yang itu: “that one friend” (contrastive/deictic—picking one among several, often when pointing).

Why is itu after the noun instead of before? Is itu teman correct for “that friend”?

In noun phrases, demonstratives follow the noun: teman itu = “that friend,” komentar itu = “that comment.”
Itu teman is a full clause meaning “that is a friend,” not “that friend.”

When would I use menertawakan instead?

Use menertawakan + object to mean “to laugh at” something/someone (often at their expense).

Aku menertawakan komentarnya. = I laughed at the comment.
Mereka menertawakan dia. = They laughed at him/her.
Your original uses a cause clause: Aku tertawa karena komentar … lucu = I laughed because the comment was funny. Don’t say menertawakan … lucu; if you need “funny,” make it a relative clause: menertawakan komentar yang lucu.

Is komentar dari teman itu also acceptable?

Yes. komentar dari teman itu = “a comment from that friend.” It’s more explicit and a bit heavier. The compact komentar teman itu is very natural. Use dari when the possessor phrase is long/complex: komentar dari teman yang kemarin kita temui.

How do I show past, present, or future in this sentence?

Indonesian doesn’t inflect for tense; add time words:

Past: Tadi/Barusan/Kemarin aku tertawa karena …
Present/progressive: Aku sedang tertawa karena …
Future/conditional: commonly use kalau (“if”): Aku akan tertawa kalau komentarnya lucu. Using karena implies the cause actually holds.

What’s a very casual way to say the same thing?

Jakarta-style casual: Gue ketawa soalnya komen temen itu lucu banget.
Changes: gue (very informal “I”), ketawa (colloquial), soalnya (casual “because”), komen (slang for komentar), temen (colloquial teman), banget (“very”).