Learn Hardcore Indonesian: Dia menolak ikut karena sedang sakit. - He/She refuses to join because he/she is ill.

No. Dia is gender-neutral and can mean he or she. Context tells you which. For a respected person, use beliau. In formal writing you may see ia (subject position only).

Why are there two verbs in a row (menolak ikut)? Don’t I need “to” before the second verb?

Indonesian commonly uses a verb followed by another bare verb as its complement. Menolak ikut literally “refused join,” i.e., “refused to join.” No linker like “to” is needed.

Do I need untuk before ikut (i.e., menolak untuk ikut)?

It’s optional. Menolak ikut is very common and natural. Menolak untuk ikut sounds a bit more formal/emphatic, but both are correct.

Can I say menolak untuk mengikuti instead of menolak ikut?

Yes, when you specify what is being joined: menolak untuk mengikuti lomba/rapat (refused to participate in the competition/meeting). Mengikuti is transitive and normally expects an object; without one, prefer ikut.

Why can the second dia be omitted in karena sedang sakit? Should I repeat the subject?

Indonesian often drops repeated subjects when clear from context. Dia menolak ikut karena sedang sakit is fine. Repeating (... karena dia sedang sakit) is also correct—just a bit heavier or extra explicit.

What does sedang add? How is sedang sakit different from just sakit, or from lagi sakit?

sedang marks a current, ongoing state: “is currently sick.”
sakit alone can simply give the reason: “because (he/she) is sick,” without highlighting the ongoing aspect.
lagi sakit is a common, more colloquial equivalent of sedang sakit. Very formal writing may use tengah sakit.

Is the sentence past or present? How do I make it clearly past?

Indonesian doesn’t mark tense by default; context decides. To make it clearly past, add a time word:

Kemarin dia menolak ikut karena sedang sakit.
Dia menolak ikut tadi pagi karena sedang sakit. You can add sudah to stress completion: Dia sudah menolak ikut...

Can I front the reason: Karena sedang sakit, dia menolak ikut? Does that change the nuance?

Yes, that’s natural. It keeps the meaning but foregrounds the cause. When the karena-clause comes first, use a comma after it.

What’s the difference between menolak, tidak mau, tidak bisa, and tidak ikut?

menolak: “refuse/decline” (deliberate, sometimes firm/formal).
tidak mau: “don’t want (to)” (softer, about willingness).
tidak bisa: “cannot/are unable (to)” (ability/permission).
tidak ikut: “didn’t/don’t join,” neutral about reason (could be refusal or inability).

What exactly does ikut mean here? Are there alternatives?

Ikut means “join/go along/attend/participate.” Alternatives by context:

hadir: attend (an event)
bergabung: join (a group/team)
turut serta/berpartisipasi: participate (more formal) Choose the one that matches the situation.

Is karena the only way to say “because”? What about gara-gara and sebab?

karena: neutral “because,” works with clauses or noun phrases.
gara-gara: informal “because of/due to,” often with a negative nuance.
sebab: formal-ish “because”; also a noun meaning “cause.”

Do I need a comma before karena?

Normally no when the karena-clause follows the main clause: Dia menolak ikut karena... If the karena-clause comes first, add a comma after it: Karena..., dia...

How can I make the sentence more polite or less direct?

Avoid menolak and use softer phrasing:

Dia berhalangan hadir karena (sedang) sakit.
Mohon maaf, dia tidak bisa ikut karena sakit. For respect: Beliau kurang enak badan (not feeling well).

Can I use bahwa after menolak (e.g., “refused that…”)?

No. Menolak means “refuse/decline (to do something)” or “reject (an offer/proposal).” For “deny that…,” use menyangkal bahwa or membantah bahwa.