Saya harus memperhatikan tanda baca ketika menulis esai.

Both mean I, but saya is more neutral and polite. It is the safest choice in standard Indonesian, writing, and formal conversation.

Aku is more informal and personal, so it is more common with friends, family, or in a casual tone.

So this sentence sounds natural and standard with saya.

Harus usually expresses a fairly strong obligation, so must or have to is the best match.

• Saya harus... = I must... / I have to...

Sometimes English translations use should if the situation sounds less strict, but the core meaning of harus is stronger than ordinary should.

If you want a softer idea like should, Indonesian often uses words like sebaiknya.

Memperhatikan means to pay attention to, to notice, or to pay careful attention to.

In this sentence:

• memperhatikan tanda baca = pay attention to punctuation

It is a standard verb that takes an object, so it is natural to learn it as a whole expression:

• memperhatikan sesuatu = to pay attention to something

Even though the word looks complicated, the most useful thing for a learner is to remember the full chunk memperhatikan + object.

Literally:

• tanda = sign / mark
• baca = read / reading

But together, tanda baca is the normal Indonesian expression for punctuation or punctuation marks.

So even if the literal parts look different from English, you should understand tanda baca as one fixed vocabulary item.

Indonesian often does not mark plural nouns unless it is necessary.

So tanda baca can mean:

• punctuation
• punctuation marks
• punctuation in general

The context tells you whether it is singular, plural, or a general category.

If a speaker really wants to emphasize plurality, they can say tanda-tanda baca, but that is not necessary here and sounds less natural in many everyday contexts.

Because Indonesian often leaves out the subject in a subordinate clause when it is already clear.

So:

• ketika menulis esai

is understood as:

• when I write an essay
• when writing an essay

The subject is still saya, but it does not need to be repeated.

If you did repeat it, ketika saya menulis esai, that would also be correct. It is just a little more explicit.

Ketika means when and introduces a time clause.

So:

• ketika menulis esai = when writing an essay / when I write an essay

It connects the action pay attention to punctuation with the situation writing an essay.

Yes. In many contexts, ketika, saat, and waktu can all mean when.

For example:

• Saya harus memperhatikan tanda baca ketika menulis esai.
• Saya harus memperhatikan tanda baca saat menulis esai.
• Saya harus memperhatikan tanda baca waktu menulis esai.

All are understandable.

A rough guide:

• ketika = slightly more formal/written
• saat = very common and natural
• waktu = common in speech, sometimes more conversational

Indonesian does not use articles like a, an, or the the way English does.

So esai by itself can mean:

• an essay
• the essay
• essays in a general sense

The context tells you which meaning is intended.

If you want to be more specific, you can add something:

• sebuah esai = an essay / one essay
• esai itu = the essay

Indonesian verbs do not change form for tense the way English verbs do.

So menulis and memperhatikan do not tell you by themselves whether the action is present, future, or habitual.

This sentence can mean something like:

• I have to pay attention to punctuation when writing essays
• I must pay attention to punctuation when I write an essay
• I will have to pay attention to punctuation when writing an essay

The time is usually understood from context, not from verb endings.

Yes. Indonesian is flexible here.

You can also say:

• Ketika menulis esai, saya harus memperhatikan tanda baca.

This means the same thing. The time clause is just moved to the front for emphasis or style.

Both versions are natural.

Yes. Esai is the Indonesian spelling of essay.

It has been adapted to Indonesian spelling, so it looks more phonetic in Indonesian.

So if you already know the English word essay, esai is easy to remember.