Ibu mengusap pipi bayi itu pelan-pelan supaya dia tenang.

Ibu most commonly means mother/mom, but it can also be a polite way to address or refer to an adult woman, similar to Mrs., ma’am, or madam.

In this sentence, Ibu most naturally means the mother.
So the subject is probably the baby’s mother.

Mengusap comes from the root usap, which means to wipe, to rub, or to stroke.

The prefix meN- makes it an active verb:

• usap = wipe/stroke
• mengusap = to wipe/stroke something

Here it means something like to gently stroke or wipe.

Because mengusap is a transitive verb, it is followed directly by its object:

• mengusap pipi bayi itu = to stroke the baby’s cheek / cheeks

In Indonesian, possession is usually shown by putting the possessed thing first and the owner after it.

So:

• pipi bayi itu = the baby’s cheek / the cheeks of that baby

This is a very common pattern:

• rumah saya = my house
• nama anak itu = that child’s name
• tangan ibu = mother’s hand

So pipi bayi itu is the normal Indonesian order.

In Indonesian, words like ini and itu usually come after the noun they describe.

So:

• bayi itu = that baby / the baby
• rumah itu = that house
• orang ini = this person

This is different from English, where this and that come before the noun.

Also, in many contexts itu can be translated not only as that, but also as the, depending on what sounds natural in English.

Indonesian often does not mark singular vs. plural explicitly unless it needs to.

So pipi can mean:

• cheek
• cheeks

The context decides.

In this sentence, English might translate it as either:

• the baby’s cheek
• the baby’s cheeks

Both are possible depending on the situation. Indonesian leaves that more open than English does.

Pelan means slow or gentle/soft, depending on context.

When it becomes pelan-pelan, the reduplication makes it sound more like an adverbial expression meaning:

• slowly
• gently
• carefully

In this sentence, pelan-pelan most naturally means gently.

Reduplication in Indonesian often changes the feel of a word or makes it sound more natural in everyday speech. It does not always mean simple plural.

Supaya means so that, in order that, or so.

It introduces the purpose or intended result of the action.

So:

• Ibu mengusap pipi bayi itu pelan-pelan supaya dia tenang means:
• The mother stroked the baby’s cheek gently so that the baby would be calm.

Other similar words are:

• agar = so that
• biar = so that / let

Supaya is very common and natural in everyday Indonesian.

Most likely, dia refers to the baby.

That is the most natural interpretation because the mother is stroking the baby’s cheek gently so that the baby becomes calm.

However, grammatically, dia can sometimes be ambiguous if there is more than one possible person in the sentence. Indonesian pronouns do not always force the same level of clarity that English does.

In real context, listeners usually understand from logic and situation.

Dia can mean:

• he
• she

Indonesian does not normally mark gender in third-person singular pronouns.

So the sentence itself does not tell you whether the baby is male or female. You only know from context, or not at all.

This is very normal in Indonesian.

In Indonesian, adjectives can often work directly as predicates without a word for is/am/are.

So:

• dia tenang = he/she is calm

There is no need for a separate verb like is.

That means:

• supaya dia tenang = so that he/she is calm / becomes calm

This is one of the biggest structural differences from English.

Indonesian verbs usually do not change form for tense.

So mengusap by itself does not mean specifically:

• stroked
• strokes
• is stroking
• will stroke

The time is normally understood from:

• context
• time words such as kemarin (yesterday), sekarang (now), nanti (later)
• the overall situation

So this sentence could be understood as past or present depending on context. English translation has to choose a tense, but Indonesian often leaves it unstated.

Indonesian does not have articles exactly like English a/an and the.

Whether something is definite or indefinite is usually understood from context.

For example:

• bayi itu clearly points to a specific baby because of itu
• Ibu may be understood as the mother from context
• pipi can be interpreted naturally in English as the cheek or the cheeks

So when translating into English, you often have to add a, an, or the, even though there is no separate Indonesian word for them.

Yes. Indonesian word order is often more flexible than English, especially with adverbs.

For example, these are all fairly natural:

• Ibu mengusap pipi bayi itu pelan-pelan supaya dia tenang.
• Ibu pelan-pelan mengusap pipi bayi itu supaya dia tenang.
• Ibu mengusap pelan-pelan pipi bayi itu supaya dia tenang.

The first version is very natural and clear.
Placing pelan-pelan after the object is common and sounds smooth in everyday Indonesian.