Penggaris kayu itu terselip di antara buku catatan saya, jadi saya lupa membawanya.

In Indonesian, demonstratives like ini and itu usually come after the noun phrase, not before it.

So:

• penggaris kayu itu = that wooden ruler
• literally: ruler wooden that

The usual order is:

noun + modifier(s) + demonstrative

Other examples:

• rumah besar itu = that big house
• buku saya itu = that book of mine

So itu is not misplaced; it is exactly where Indonesian normally puts it.

Yes. In Indonesian, words that describe a noun usually come after the noun.

So:

• penggaris kayu = wooden ruler
• literally: ruler wood

Here kayu is a noun meaning wood, but it functions like a material descriptor, similar to an adjective in English.

Compare:

• meja kayu = wooden table
• sendok plastik = plastic spoon
• gelang emas = gold bracelet

English often puts this kind of word before the noun, but Indonesian usually puts it after.

Terselip means something like got tucked, got wedged, got slipped into a place, or was stuck in between by accident.

It comes from the root selip, which has the idea of slipping or being inserted into a narrow space.

The prefix ter- often gives the sense of:

• a resulting state
• something accidental or unintentional
• something that ended up in a certain position

So penggaris kayu itu terselip di antara buku catatan saya suggests:

• the ruler ended up stuck between the notebooks
• it was not necessarily placed there deliberately
• the speaker is describing its position/state

A natural English translation is often:

• That wooden ruler was tucked in between my notebooks
• That wooden ruler had gotten stuck between my notebooks

Not exactly in the same way as a standard passive like dibawa.

In terselip, ter- does not mainly mean was X-ed by someone. Instead, it often describes a state or an accidental event.

Compare:

• dibuka = opened / was opened
  → regular passive idea
• terbuka = open / accidentally opened / ended up open
  → state or accidental result

So terselip is better understood as:

• was tucked/stuck
• got wedged
• ended up slipping in

It focuses more on the situation than on who caused it.

Di antara means between or among in a location sense.

• di = a preposition meaning in/at/on
• antara = between/among

Together, di antara means in between or among.

So:

• di antara buku catatan saya = between my notebooks

You will sometimes see antara without di, but that usually happens in other structures, especially when antara is not functioning as a simple location phrase.

Examples:

• di antara dua rumah = between two houses
• antara A dan B = between A and B

In this sentence, because it describes location, di antara is the normal choice.

Indonesian noun phrases usually go from the main noun to the modifiers.

Here:

• buku catatan = notebook
  literally book notes
• buku catatan saya = my notebook(s)

The order is:

noun + describing noun + possessor

So:

• buku catatan saya = my notebook(s)
• rumah teman saya = my friend’s house
• nama guru itu = that teacher’s name

English often uses possessives earlier, but Indonesian usually puts saya, dia, mereka, etc. after the noun phrase.

Grammatically, it can be ambiguous without extra context.

Buku catatan saya could mean:

• my notebook
• my notebooks

In this sentence, because the ruler is di antara them, English often interprets it as plural: between my notebooks. But Indonesian does not always mark plurals explicitly.

If the speaker really wanted to make the plural very clear, they could say:

• buku-buku catatan saya

But in normal Indonesian, leaving it as buku catatan saya is very natural.

Here jadi means so, therefore, or as a result.

It connects the first clause to the result in the second clause:

• Penggaris kayu itu terselip di antara buku catatan saya, jadi saya lupa membawanya.
• The wooden ruler was tucked between my notebooks, so I forgot to bring it.

In other contexts, jadi can also mean:

• to become
• to be finished / done
• so (as a connector)

But in this sentence, it is clearly the connector meaning so.

Membawanya breaks down as:

• membawa = to bring
• -nya = it / him / her

Here -nya refers to penggaris kayu itu.

So saya lupa membawanya means:

• I forgot to bring it

This -nya is a very common object pronoun suffix in Indonesian.

Compare:

• Saya melihatnya. = I saw him/her/it.
• Dia membacanya. = He/She read it.

In your sentence, -nya is best translated as it, because it refers to the ruler.

Membawa is the standard active verb form.

It comes from the root:

• bawa = bring / carry

With the prefix meN-, it becomes:

• membawa = to bring

In formal and neutral written Indonesian, membawa is the normal form in a sentence like this:

• saya lupa membawanya

In casual speech, people may sometimes use the root form:

• saya lupa bawa itu

But membawanya is more complete and standard.

In Indonesian, after lupa (to forget), it is very common to put the following verb directly, without untuk.

So these are both possible:

• Saya lupa membawanya.
• Saya lupa untuk membawanya.

But the version without untuk is usually more natural and more common.

So:

• lupa membawa... = forget to bring...

The same thing happens with many other verbs in Indonesian, where English might use to, but Indonesian often just places the next verb directly after the first one.

Yes, but membawanya sounds smoother and more natural here.

Compare:

• saya lupa membawanya = I forgot to bring it
• saya lupa membawa itu = I forgot to bring that

Using -nya is common when the object has already been mentioned and is understood. It works a lot like saying it in English instead of repeating that ruler.

So in this sentence, membawanya is the more natural choice.

It is not absolutely required in every informal context, but it is very natural and helpful in writing because the sentence has two clauses:

1. Penggaris kayu itu terselip di antara buku catatan saya
2. jadi saya lupa membawanya

The comma helps show the pause and the cause-result relationship.

So this version is very natural:

• Penggaris kayu itu terselip di antara buku catatan saya, jadi saya lupa membawanya.

Without the comma, people would still understand it, but the punctuation with the comma is clearer.

Yes, it is natural and correct.

It sounds like a normal explanation of why the speaker forgot to bring the ruler. The flow is clear:

1. the ruler was stuck between the notebooks
2. as a result, the speaker forgot to bring it

A few possible variations are also natural, for example:

• Penggaris kayu itu terselip di antara buku catatan saya sehingga saya lupa membawanya.
  More formal, using sehingga = so / therefore

• Penggaris kayu itu terselip di antara buku-buku catatan saya, jadi saya lupa membawanya.
  Makes the plural notebooks more explicit

But the original sentence is already perfectly good Indonesian.