Learn Hardcore Indonesian: Ibu tidak hadir kemarin karena ada rapat lain. - Mother did not attend yesterday because there was another meeting.

As a kinship term: ibu = mother. Then you’d usually say ibu saya (my mother).
As an honorific/title for an adult woman (teacher, boss, respected lady): Ibu (often written uppercase when it’s a title or at sentence start), e.g., Ibu Sari = Ms./Mrs. Sari. You can also just say Ibu to refer to a known female superior.
Colloquial short form: Bu.

Without more context, the sentence could mean “Mother wasn’t present…” or “Ma’am/Ms. (the female teacher/boss) wasn’t present…”.

Why is tidak used instead of bukan?

tidak negates verbs and adjectives: tidak hadir = not present/did not attend.
bukan negates nouns and pronouns: Itu bukan rapat = That is not a meeting. Since hadir is a verb-like predicate (“be present/attend”), you use tidak.

Is hadir a verb or an adjective? Could I use datang instead?

hadir means “to be present/attend” (stative/verb-like). tidak hadir = didn’t attend/absent.
datang = to come. tidak datang = didn’t come/show up. Nuance:
hadir is slightly more formal and event/attendance-focused.
datang is neutral/casual and movement-focused. Both work, but hadir matches “attendance” contexts well.

How is the past tense shown? Do I need sudah/telah?

Indonesian doesn’t change the verb for tense. Time words do the job:

kemarin = yesterday → past time is clear. You can add aspect markers if you want:
sudah/telah emphasize completion, e.g., Beliau sudah hadir. Here it’s unnecessary: Ibu tidak hadir kemarin is natural.

What does ada mean in karena ada rapat lain? Is it “have”?

Here ada is existential: “there is/was.”

karena ada rapat lain = because there was another meeting. To express “have,” use a subject with punya:
karena dia punya rapat lain = because she had another meeting. Colloquially, many say dia ada rapat (“she has a meeting”), but in formal writing prefer punya or a clearer verb phrase: harus menghadiri rapat lain (had to attend another meeting).

What does lain add? Is it “another” or “different,” and where does it go?

lain = other/another/different.
Position: after the noun → rapat lain = another/different meeting. Related forms:
yang lain = the other(s)/the rest (pronoun-like): yang lain sudah pulang.
lainnya = the other one(s)/the rest (more definite): rapat lainnya.
rapat yang lain = the other meeting (among known options), a bit more specific than rapat lain.

Can I change the word order? Where can kemarin go? Do I need a comma?

Yes, several natural options:

Ibu tidak hadir kemarin karena ada rapat lain.
Kemarin Ibu tidak hadir karena ada rapat lain. (fronts the time = emphasis on “yesterday”)
Ibu kemarin tidak hadir karena ada rapat lain. (common in speech) If the because-clause comes first, use a comma:
Karena ada rapat lain, Ibu tidak hadir kemarin.

Is there a more casual or more formal way to say this?

Casual:

Ibu kemarin nggak/gak hadir karena ada rapat lain.
Ibu kemarin nggak datang karena ada rapat lain.
Ibu kemarin nggak masuk (for work/school contexts). Formal/neutral:
Ibu tidak bisa hadir kemarin karena ada rapat lain.
Beliau berhalangan hadir kemarin karena ada rapat lain.

Should I say tidak bisa hadir to show she couldn’t attend?

tidak hadir states the fact: she did not attend.
tidak bisa hadir adds inability: she couldn’t attend. With a reason like another meeting, both are fine; tidak bisa hadir makes the constraint explicit.

Do I need an article or classifier before rapat? What about satu/sebuah?

No articles in Indonesian. ada rapat lain already conveys “another meeting.”

Avoid satu rapat lain (ungrammatical).
If you mean “one more meeting,” say satu rapat lagi or more naturally ada satu rapat lagi.

What’s the difference between karena, sebab, and gara-gara?

karena = because (neutral, most common).
sebab = cause/because (more formal/literary as a conjunction).
gara-gara = because of/thanks to (colloquial, often for negative/unwanted causes): Ibu nggak hadir gara-gara rapat lain.

Can I replace Ibu with a pronoun like dia or beliau?

Yes:

Dia tidak hadir kemarin karena ada rapat lain. (neutral “he/she”)
Beliau tidak hadir kemarin karena ada rapat lain. (beliau is respectful/polite for elders or people of higher status; not for peers/children.)

If I mean “my mother,” how should I say it? Does capitalization matter?

Use a possessor:

Ibu saya tidak hadir kemarin karena ada rapat lain. In many contexts you might prefer datang for “came”: Ibu saya kemarin tidak datang karena ada rapat lain. Capitalization:
When ibu is a common noun (mother in general), it’s often lowercase unless it starts the sentence: ibu saya.
As a title/honorific before a name, capitalize: Ibu Sari.

Is kemarin strictly “yesterday,” or can it mean “the other day”?

Literally it’s “yesterday,” but in casual speech it can stretch to “the other day/recently.” For clarity:

Day before yesterday: kemarin lusa.
A few days ago: beberapa hari yang lalu.
Earlier today: tadi (e.g., tadi pagi).

Can I drop ada and say karena rapat lain?

Yes, especially in speech: Ibu tidak hadir kemarin karena rapat lain. It’s an elliptical “because of another meeting.” Using ada makes the cause a full clause (“because there was another meeting”), which can feel a bit clearer or more neutral in writing.

Any quick pronunciation tips?

Ibu: “EE-boo”
tidak: “TEE-dahk” (final k is a glottal stop)
hadir: “HAH-deer”
kemarin: “kə-MA-rin” (first e like a schwa)
rapat: “RAH-pa(t)” (final t unreleased)
lain: “LA-in” (two syllables: la-in)