Bayi itu tidur di riba ibu.

In Malay, demonstratives like ini and itu normally come after the noun.

So:

• bayi itu = that baby / the baby
• rumah itu = that house
• buku ini = this book

This is the normal Malay word order, even though English puts this/that before the noun.

It can mean either, depending on context.

In many sentences, itu makes the noun specific or already identifiable. Because of that, English may translate bayi itu as:

• that baby
• the baby

So itu is not always as strongly demonstrative as English that. Sometimes it simply helps mark something as known in the conversation.

Malay often does not use a separate word like English is/am/are in this kind of sentence.

Here, tidur is already the verb to sleep, so:

• Bayi itu tidur = The baby sleeps / The baby is sleeping

You do not need an extra verb like is before tidur.

By itself, tidur can cover all of those, depending on context.

Malay verbs do not change form the way English verbs do. So:

• tidur can mean sleep
• tidur can mean sleeps
• tidur can mean is sleeping

The exact time or aspect usually comes from context or time words, not from changing the verb itself.

No, not directly. Malay does not usually mark tense on the verb.

So Bayi itu tidur di riba ibu could mean:

• The baby is sleeping in mother's lap
• The baby sleeps in mother's lap
• in the right context, even The baby slept in mother's lap

If you want to make time clearer, Malay often adds time words such as:

• sedang for an ongoing action
• sudah for a completed action
• akan for a future action

For example:

• Bayi itu sedang tidur = The baby is sleeping

Because this di is a preposition, not a prefix.

As a preposition, di means something like at, in, or on, and it is written as a separate word:

• di rumah
• di sekolah
• di riba

This is different from the passive prefix di-, which is attached directly to a verb:

• ditulis = written
• dibuka = opened

So in this sentence, di riba is correct because di is showing location.

Here, di marks a location.

In English, the best translation depends on the noun that follows. With riba (lap), English usually says:

• on the lap
• sometimes in the lap

So di riba ibu means on/in mother's lap.

Riba means lap, especially the place where someone can hold a child while sitting.

It often appears in phrases like:

• di riba ibu = in/on mother's lap
• di ribanya = in/on his/her lap

So this sentence gives the image of the baby sleeping while being held on the mother's lap.

Because Malay usually expresses possession with the order:

thing possessed + possessor

So:

• riba ibu = mother's lap
• rumah Ali = Ali's house
• buku saya = my book

Literally, riba ibu is something like lap mother, but in natural English we translate it as mother's lap.

Not necessarily. Malay often leaves that kind of relationship to context.

So ibu here can simply mean mother, with the sentence understood naturally as referring to the relevant mother in context.

If a speaker wanted to make the possession more explicit, they might say:

• di riba ibunya = in his/her mother's lap
• di riba ibu bayi itu = in the baby's mother's lap

But the shorter di riba ibu is still understandable, especially when the situation is clear.

Yes. Ibu can also be used as a respectful form of address, similar to madam in some contexts.

However, in di riba ibu, the most natural meaning is definitely mother, because lap strongly suggests a family or caregiving context.

Yes. It follows a very normal pattern:

Bayi itu — subject
tidur — verb
di riba ibu — location phrase

So the sentence structure is basically: Subject + Verb + Place

That makes this a very natural and straightforward Malay sentence.