Learn Hardcore Indonesian: Turnamen voli antar-kelas membuat teman perempuan saya lebih rajin berlatih. - The inter-class volleyball tournament makes my female friend practice more diligently.

Antar-kelas literally means between classes / inter-class, so turnamen voli antar-kelas is an inter-class volleyball tournament (a tournament between school classes).

About the writing:

antar by itself means between / among.
When it acts like an English prefix inter-, many writers (and recent spelling guides) prefer writing it together with the next word: antarkelas.
You will also see antar kelas (two words) and antar-kelas (with a hyphen) in real life. All are easily understood.

So in your sentence, antar-kelas is functioning like inter-class in English.

Why is the order turnamen voli antar-kelas and not something like antar-kelas turnamen voli?

In Indonesian, the typical pattern is:

Head noun + describing words (modifiers)

So:

turnamen = tournament (head noun)
voli = volleyball (what kind of tournament?)
antar-kelas = inter-class (what kind of volleyball tournament?)

They stack after the head noun:

turnamen (tournament)
turnamen voli (volleyball tournament)
turnamen voli antar-kelas (inter-class volleyball tournament)

Putting antar-kelas in front (like antar-kelas turnamen) would sound wrong or at least very odd to native speakers. In Indonesian, descriptive elements almost always go after the noun, unlike in English.

Is there any difference between voli and bola voli?

Both refer to the sport of volleyball:

voli = volleyball
bola voli = literally volleyball ball, but used to mean the sport of volleyball as well

Usage:

In many casual contexts, people just say voli:
- Main voli = play volleyball
Bola voli can sound slightly more formal or explicit, and is common in written contexts, sports news, or school contexts.

You could say either:

Turnamen voli antar-kelas
Turnamen bola voli antar-kelas

Both are fine and natural.

Can teman perempuan saya mean my girlfriend, or is it only my female friend?

Literally, teman perempuan saya means my female friend:

teman = friend
perempuan = female / woman
saya = my

Whether it can mean girlfriend depends on context, tone, and situation:

In many contexts, it is understood as just a friend who is female.
Sometimes, especially in speech and with certain intonation or context, it can be taken to mean girlfriend, but it is not automatically romantic.

For a clearly romantic partner, Indonesians more often say:

pacar saya = my boyfriend / my girlfriend (gender-neutral)
cewek saya (very colloquial, literally my girl)
cowok saya for my boyfriend (colloquial)

So, teman perempuan saya is safest to understand as my female friend unless the context clearly suggests romance.

Does teman perempuan saya mean my female friend (singular) or my female friends (plural)?

By itself, teman perempuan saya is number-neutral: it can be read as my female friend or my female friends, depending on context.

Indonesian usually does not mark singular vs plural explicitly. If you want to make plural clear, you can say:

teman-teman perempuan saya = my female friends
(reduplication teman-teman shows plurality)

So:

teman perempuan saya lebih rajin berlatih
could be interpreted as my female friend or my female friends became more diligent in practicing, depending on the situation.

If you specifically want one female friend, context or extra words can help:

seorang teman perempuan saya = one female friend of mine

How does membuat work in this sentence? Why is it membuat teman perempuan saya lebih rajin berlatih?

Here membuat is used in a causative sense, like English to make / to cause:

Pattern:

membuat + [person] + [adjective / verb phrase]

Meaning:

to make [person] [adjective / do something]

In this sentence:

membuat = makes / made
teman perempuan saya = my female friend
lebih rajin berlatih = more diligent in practicing

So the structure is:

Turnamen voli antar-kelas
membuat (caused)
teman perempuan saya (my female friend)
lebih rajin berlatih (to be more diligent about practicing).

This is very natural Indonesian; you do not need an extra word like untuk or agar here.

Why is it lebih rajin berlatih, not lebih rajin untuk berlatih? Is untuk wrong?

The most natural phrasing is:

lebih rajin berlatih

You could say:

lebih rajin untuk berlatih

but it often sounds heavier or slightly less natural in everyday speech, especially after membuat.

Rough feel:

lebih rajin berlatih – smooth, typical, very natural.
lebih rajin untuk berlatih – can be used, but tends to sound more formal or a bit wordy, and many natives would simply drop untuk.

In general, when a verb follows another verb like mulai, suka, ingin, coba, rajin, etc., Indonesian often just puts the second verb directly after it:

rajin belajar (diligent in studying)
rajin membantu (diligent about helping)
rajin berlatih (diligent about practicing)

So lebih rajin berlatih is the clean, natural form.

What nuance does rajin have? Is it just diligent?

Rajin is close to diligent, but its nuance includes:

hard-working, consistent, and active in doing something, often with a sense of frequency and willingness.
It can be used for study, work, chores, religious practice, sports, etc.

Examples:

Dia rajin belajar. = He/She studies diligently / is a hard-working student.
Anak itu rajin membantu orang tua. = That child often and willingly helps their parents.
Mereka rajin berlatih setiap sore. = They practice regularly every afternoon.

Lebih rajin berlatih means they practice more often / more seriously / with more effort than before. It’s a comparative: more diligent about practicing.

What is the difference between berlatih and latihan?

Both are related to practice, but they are different word types:

berlatih – a verb: to practice
- Kami berlatih setiap hari. = We practice every day.
latihan – a noun: practice / training / exercise
- Kami ada latihan setiap hari. = We have practice every day.
- Latihan hari ini capek sekali. = Today’s practice was exhausting.

In your sentence, you need a verb phrase:

lebih rajin berlatih = more diligent in practicing.

If you used latihan directly there, it would be ungrammatical as-is:

✗ lebih rajin latihan is not standard in careful Indonesian (some people say it colloquially, but berlatih is the correct form).

How do I know if this sentence is past, present, or future? There is no tense marker.

Indonesian verbs do not change form for tense. Membuat can mean:

makes (present)
made (past)
will make (future)

The time is usually clear from context or extra words.

To be explicit, you can add time markers:

Kemarin, turnamen voli antar-kelas membuat teman perempuan saya lebih rajin berlatih.
= Yesterday, the inter-class volleyball tournament made my female friend more diligent in practicing. (past)
Sekarang, turnamen voli antar-kelas membuat teman perempuan saya lebih rajin berlatih.
= Now, the tournament is making my female friend more diligent in practicing. (present)
Besok, turnamen voli antar-kelas akan membuat teman perempuan saya lebih rajin berlatih.
= Tomorrow, the tournament will make my female friend more diligent in practicing. (future, akan makes future explicit)

In the bare form you gave, context would decide whether we understand it as talking about now, about a recent experience, or a general fact.

Is there another natural way to say this sentence, maybe using menjadi instead of membuat?

Yes. You can rephrase it more subject-focused by using menjadi:

Karena turnamen voli antar-kelas, teman perempuan saya menjadi lebih rajin berlatih.

Breakdown:

Karena = because of
menjadi = to become

Meaning: Because of the inter-class volleyball tournament, my female friend became more diligent about practicing.

Comparison:

Turnamen … membuat teman perempuan saya lebih rajin berlatih.
Focus: the tournament caused the change.
Teman perempuan saya menjadi lebih rajin berlatih karena turnamen ….
Focus: my female friend changed / became more diligent, and the reason is the tournament.

Both are natural; they just have slightly different emphases.