Learn Hardcore Indonesian: Saat pertunjukan selesai, penyanyi membagikan jeruk manis kepada penonton. - When the performance ends, the singer hands out sweet oranges to the audience.

Saat here means “when” and introduces the time clause “when the show finished.” You can indeed replace Saat with Ketika without changing the meaning:
“Ketika pertunjukan selesai, penyanyi membagikan jeruk manis kepada penonton.”
Using Setelah shifts it slightly—Setelah means “after,” so you would need to adjust the clause:
“Setelah pertunjukan selesai, penyanyi membagikan jeruk manis kepada penonton.”
All three are correct, but Ketika/Saat focus on “at the moment it ended,” while Setelah emphasizes “after it ended.”

Why is selesai placed after pertunjukan? Is it an adjective or a verb?

Here selesai acts like an adjective meaning “finished” (although it can also be a verb). In Indonesian, adjectives and certain verb‐like words typically follow the noun they modify. So pertunjukan selesai literally is “show finished.” If you wrote selesai pertunjukan, it would sound awkward because the modifier usually comes after the noun in this pattern.

What does penyanyi mean and how is it formed?

Penyanyi means “singer.” It’s formed from the root verb nyanyi (“to sing”) plus the agent‐forming prefix pe- (which becomes pen- before n) and the suffix -i. Together they create a noun that denotes “one who sings.”

What is membagikan, and how is it different from membagi or memberi?

Membagikan is a verb meaning “to distribute” or “to hand out.” It consists of the prefix mem-, the root bagi (“to divide/share”), and the suffix -kan, which often indicates causing something to happen or transferring something to someone.

Membagi (mem- + bagi) also means “to divide/share,” but without the suffix -kan it’s more focused on the division process itself.
Memberi (mem- + beri “to give”) simply means “to give.” You’d use memberi for giving a single item or for a direct gift: “penyanyi memberi hadiah.”
You choose membagikan when you want to emphasize handing out multiple items to recipients.

Why is kepada used before penonton? Could I use ke or untuk instead?

Kepada marks the recipient (to whom something is given).

Ke is a directional preposition (“to/toward a place”), not for recipients.
Untuk indicates purpose or beneficiary (“for”), but you’d more naturally say untuk penonton if you meant “intended for the audience,” not “handed out to them.”
So for “hand out to the audience,” kepada penonton is the correct choice.

Why doesn’t jeruk manis have a plural marker? How do we show plurality in Indonesian nouns?

Indonesian nouns are generally unmarked for number. Jeruk manis could mean one sweet orange or many, depending on context. Here the act of distribution implies multiple fruits. If you need to be explicit, you add a quantifier or numeral:

beberapa jeruk manis (several sweet oranges)
dua belas jeruk manis (twelve sweet oranges)

Can penonton refer to a single person, or is it always plural?

Penonton is neutral on number—it can mean “a spectator” or “spectators” as a group. To specify a single person, you can say seorang penonton or satu penonton. For clarity about multiple people, you can use quantifiers like banyak penonton (many spectators).

How can I rewrite this sentence in the passive voice?

You can promote jeruk manis (the object) to subject position and insert oleh before the agent:
“Saat pertunjukan selesai, jeruk manis dibagikan oleh penyanyi kepada penonton.”
Or more succinctly:
“Saat pertunjukan selesai, jeruk manis dibagikan penyanyi kepada penonton.”
Both are acceptable in Indonesian passive constructions.