Guru itu tidak galak, tetapi beliau tegas ketika ada murid yang berbohong.

Indonesian often leaves out the verb to be in simple present statements.

So:

• Guru itu tidak galak = That teacher is not fierce/mean
• literally, it looks more like Teacher that not fierce

This is completely normal in Indonesian. Adjectives can act as the predicate without needing a separate is/are.

Here, itu means something like that or the one we’re talking about.

So guru itu can mean:

• that teacher
• the teacher (when the person is already known in the conversation)

In Indonesian, itu often comes after the noun:

• guru itu = that teacher
• murid itu = that student

This is different from English word order.

Use tidak to negate:

• verbs
• adjectives

Use bukan to negate:

• nouns
• noun phrases

Since galak is an adjective, tidak is correct.

Examples:

• Dia tidak galak = He/She is not fierce
• Dia bukan guru = He/She is not a teacher

So bukan galak would sound wrong in standard Indonesian.

Not exactly.

Galak usually means:

• fierce
• harsh
• intimidating
• quick to scold
• mean in manner

It often describes someone who seems severe in an unpleasant way.

By contrast, tegas means:

• firm
• assertive
• clear and disciplined

So the sentence contrasts two ideas:

• the teacher is not harsh/mean
• but the teacher is firm when needed

That distinction is very important.

This sentence is built around that contrast.

• galak = harsh, fierce, scary, sharp in attitude
• tegas = firm, decisive, not soft when enforcing rules

A galak teacher may feel unpleasant or overly aggressive. A tegas teacher may be strict, but in a fair and controlled way.

So the sentence suggests a positive image: the teacher is not bad-tempered, just firm when students lie.

Beliau is a respectful third-person pronoun, used for someone you want to speak about politely.

It is commonly used for:

• teachers
• elders
• respected figures
• officials
• community leaders

So:

• dia = he/she (neutral, everyday)
• beliau = he/she (respectful)

Because the sentence is about a teacher, beliau sounds polite and appropriate.

Yes. That is exactly what it is doing here.

The sentence first introduces the person:

• Guru itu = that teacher

Then it refers to the same person politely:

• beliau = he/she, respectfully

This is very natural in Indonesian. It avoids repeating guru itu and also shows respect.

Yes, you can say tapi in everyday speech.

• tetapi = but/however, more formal or careful
• tapi = shorter, more conversational

So both are possible:

• Guru itu tidak galak, tetapi beliau tegas...
• Guru itu tidak galak, tapi beliau tegas...

The meaning stays the same. Tetapi just sounds a bit more formal or polished.

Ketika means when.

In this sentence:

• ketika ada murid yang berbohong = when there is a student who lies / when a student lies

Possible alternatives:

• saat = when, at the time when
• waktu = when
• kalau = if/when, but often less specific and more conversational

Examples:

• ...tegas ketika ada murid yang berbohong
• ...tegas saat ada murid yang berbohong

Both sound natural.

Kalau is possible in some contexts, but ketika fits better here because it clearly means a time/situation, not a condition.

Ada here means there is/there are or indicates the existence of someone in a situation.

So:

• ketika ada murid yang berbohong = when there is a student who lies / when any student lies

This structure is very common in Indonesian. It introduces the presence of someone in a certain situation.

Without ada, the sentence would feel different and less natural in this context.

Yang introduces a relative clause. It works like who, that, or which in English.

So:

• murid yang berbohong = the student who lies or a student who lies

Breakdown:

• murid = student
• yang = who/that
• berbohong = lies / is lying

This is one of the most common uses of yang in Indonesian.

Bohong and berbohong are related, but they are not exactly the same in form.

• bohong can function as false, a lie, or colloquially lying
• berbohong is the verb to lie

So in more standard grammar:

• murid yang berbohong = students who lie

In casual Indonesian, people may also say:

• murid yang bohong

But berbohong is the clearer and more standard verbal form.

The prefix ber- often forms intransitive verbs, especially verbs describing an action or state performed by the subject.

So:

• bohong = lie, falsehood, false
• berbohong = to tell lies / to lie

You do not need to translate ber- by itself every time. It is better to learn the whole word:

• berjalan = to walk
• berbicara = to speak
• berbohong = to lie

By itself, guru can be singular or plural. Indonesian nouns usually do not change form for number.

But in this sentence, it is understood as singular because of the context:

• guru itu = that teacher / the teacher
• beliau also refers to one person

If it were plural, the sentence would need clearer context or wording.

In this sentence, it most naturally means any student who lies or a student who lies in that situation.

Because of ada, the meaning is not necessarily one specific student already known to the listener. It is more general:

• whenever there is a student who lies
• when a student lies

So the sentence describes the teacher’s behavior in that kind of situation.

Yes, that is a close literal translation.

A more natural English version might be:

• That teacher isn’t harsh, but is firm when a student lies.
• The teacher is not mean, but is firm when a student lies.

The Indonesian sentence sounds natural, even if the most literal English version feels slightly stiff.

It is mostly neutral to fairly polite.

Features that make it sound polite or slightly formal:

• beliau instead of dia
• tetapi instead of tapi
• ketika instead of a more casual alternative

So it would fit well in:

• writing
• school-related discussion
• respectful description of a teacher

It is not extremely formal, but it is definitely not slangy.