Learn Hardcore Indonesian: Saya mengganti baju sebelum rapat.

Yes. Mengganti is more formal/standard; ganti is very common in everyday speech. Both are natural. In careful writing, prefer mengganti; in conversation, ganti is fine.

What’s the difference between mengganti, berganti, and ganti?

mengganti [object]: transitive, standard. Example: Saya mengganti baju.
ganti [object]: colloquial drop of the prefix. Example: Saya ganti baju.
berganti: intransitive “to undergo a change,” but with clothing it’s acceptable and a bit more formal: Saya berganti baju/pakaian. Also used without an object: Musim berganti.

Does baju mean “shirt” or “clothes”?

In daily Indonesian, baju often means “clothes” or a top garment. For “shirt” specifically, use kemeja. For “clothing” in a general or formal sense, use pakaian. Mengganti baju means “to get changed.”

Is pakaian better than baju here?

Both are correct. Baju is everyday and neutral. Pakaian sounds more formal or generic. For a polished tone: Saya berganti pakaian sebelum rapat.

How do I say “I changed my shirt” versus “I changed clothes”?

Changed clothes: Saya ganti/mengganti baju.
Changed my shirt: Saya mengganti kemeja (saya). Possessives are often omitted when obvious; add saya for clarity only if needed.

How do I express “change A to/for B”?

Use mengganti [A] dengan [B].

Saya mengganti kaus dengan kemeja sebelum rapat. Avoid mengubah with clothes; that means “alter/modify,” not “change into.”

How do I say “before the meeting started” more explicitly?

Sebelum rapat already implies “before the meeting (started).” To be explicit: sebelum rapat dimulai. Note sebelumnya means “previously” and doesn’t take a noun after it.

How do I make “the meeting” definite, like “that specific meeting”?

Indonesian has no articles. Make it definite with context markers:

sebelum rapat itu (that meeting)
sebelum rapat tadi (the earlier meeting)
sebelum rapatnya (the meeting in question)

Can I put the time phrase first?

Yes. Sebelum rapat, saya mengganti baju. Fronting time expressions is natural; use a comma when fronted.

How do I negate it? “I didn’t change clothes before the meeting.”

Use tidak to negate the verb: Saya tidak ganti/mengganti baju sebelum rapat. Don’t use bukan here.

How do I say “I’m changing clothes right now before the meeting”?

Use a progressive marker: Saya sedang ganti/mengganti baju sebelum rapat. Colloquial: Saya lagi ganti baju sebelum rapat.

Is rapat the right word for a work meeting? What about pertemuan?

Rapat is the standard word for a work or formal meeting (e.g., rapat tim, rapat bulanan). Pertemuan is a meeting in the sense of a gathering or encounter, not necessarily workplace. In business slang, people also say meeting, but rapat is best here.

Can I drop saya?

You can if context is clear. Mengganti baju sebelum rapat could read like a fragment or general instruction. As an imperative, drop it and use: Ganti baju sebelum rapat.

Any quick pronunciation tips?

mengganti: məng-GAN-ti (hard g; ng as in “singer”). The ngg comes from the prefix.
sebelum: sə-bə-LUM (the e is a schwa).
rapat: RA-pat (final t is crisp, not aspirated).

How can I make the sentence more formal?

Use more formal choices: Sebelum rapat, saya berganti pakaian. For completed action in formal writing: Saya telah berganti pakaian sebelum rapat.

Is tukar baju okay?

Be careful. Bertukar baju usually means exchanging clothes with someone else. For changing your own clothes, say ganti/mengganti baju or berganti pakaian.

What’s the passive version and what does it imply?

Baju saya diganti sebelum rapat. This means “My clothes were changed,” implying someone else changed them. It’s natural for talking about a child or patient, but odd if you mean you changed yourself.

Could rapat here mean “tight/close”?

No. In this context it’s clearly the noun “meeting.” The adjective meaning “tight/close” appears in phrases like tutup rapat, which is unrelated here.

Do I ever need a preposition before rapat here?

Not with sebelum. Say sebelum rapat, not sebelum di rapat. Use di for places: di ruang rapat (in the meeting room).