Kalau telepon berdering saat saya tidur siang, saya tidak akan mengangkatnya.

If the phone rings while I am taking a nap, I will not answer it.

Breakdown of Kalau telepon berdering saat saya tidur siang, saya tidak akan mengangkatnya.

• saya: I
• tidak: not
• akan: will
• nya: it
• kalau: if
• berdering: to ring
• telepon: telephone/phone
• tidur siang: to take a nap
• saat: while/when
• mengangkat: to answer (the phone)

Questions & Answers about Kalau telepon berdering saat saya tidur siang, saya tidak akan mengangkatnya.

What does kalau mean here, and how is it different from jika?

Kalau introduces a condition: if/when. In everyday Indonesian, kalau is very common and conversational. Jika is also if, but it tends to sound more formal/written. In this sentence, kalau could be replaced by jika with no real change in meaning, just a slightly more formal tone.

Why is there a comma after kalau telepon berdering saat saya tidur siang?

The comma separates the conditional clause (the if part) from the main clause (the result). This mirrors English punctuation in many cases: If X, then Y. In Indonesian writing, the comma is commonly used this way, especially when the conditional clause comes first.

Does kalau mean if or when? Which one should I understand it as?

It can be either, depending on context. Here, it’s a general situation/habit, so it’s very natural to understand it as if/whenever: whenever the phone rings during my nap, I won’t pick it up.

What exactly does telepon berdering mean? Is it a verb phrase?

Yes. Telepon = phone, berdering = to ring (to make a ringing sound). Together: the phone rings.
ber- is a common verb prefix that often forms intransitive verbs (actions that happen without a direct object), and berdering is used specifically for things like phones, alarms, bells.

Can I also say teleponnya berdering? What’s the difference?

Yes. Teleponnya berdering means his/her/the phone rings depending on context (because -nya can mark possession or something definite).
Telepon berdering is more general: (the) phone rings without specifying whose phone, and it sounds neutral.

Why use saat here? How is it different from ketika or waktu?

All three can mean when.

• saat is common and fairly neutral, often used for at the time when.
• ketika is also when, sometimes a bit more narrative/story-like.
• waktu can mean time and also when, but it can sound slightly more general.
  In this sentence, saat fits well and could be replaced by ketika with little change.

Does saya tidur siang literally mean I sleep noon? How should I think about it?

Tidur siang is a fixed phrase meaning to take a nap / to nap (in the daytime).
So saat saya tidur siang = while/when I’m taking a nap.

Why is akan used in saya tidak akan mengangkatnya? Is this future tense?

Indonesian doesn’t have mandatory tense marking like English, but akan often expresses future or intended/would action. In a conditional sentence like this, tidak akan is very natural for won’t / wouldn’t:

• saya tidak akan mengangkatnya = I won’t pick it up / I wouldn’t answer it (depending on context).

What does mengangkatnya mean literally, and why does it mean answer (the phone)?

Literally, mengangkat means to lift/raise. For phones, Indonesian commonly uses mengangkat telepon = to pick up the phone, which equals to answer the phone.
The -nya at the end (mengangkatnya) means pick it up / answer it, where it refers to the phone.

What exactly is the -nya in mengangkatnya referring to, and can I drop it?

Here -nya is an object pronoun meaning it (referring to telepon). You can say:

• saya tidak akan mengangkat = I won’t pick up (it)
  This is grammatical if the object is obvious from context, but adding -nya makes it explicit: I won’t pick it up.

Is there a more natural way to say this in everyday Indonesian?

This sentence is already natural. Very common alternatives include:

• Kalau telepon berdering pas aku tidur siang, aku nggak akan angkat. (more casual: pas, aku, nggak, drop -nya)
• Kalau ada telepon waktu aku lagi tidur siang, aku nggak akan angkat. (adds ada telepon = if there’s a call)

Why is mengangkat used instead of menjawab?

Menjawab means to answer (a question, or sometimes a phone), but for phones, Indonesian very commonly prefers angkat (telepon) / mengangkat (telepon) for pick up/answer the phone.
Menjawab telepon is understandable, but mengangkat telepon often sounds more idiomatic.